big bullets for beginners

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Big Bullets for Beginners Guns are generally classified according to use, size, and tradition. This varies among the military services. The basic distinction is between small arms and artillery. Any gun below a 20-millimeter bore size is generally classified as a small arm. The US Army distinguishes among mortars, howitzers, and guns. Mortars give high trajectories with short range and are usually loaded from the muzzle. Howitzers give medium-to-high trajectories, and guns provide flat-to-medium trajectories of longer range. Bore size is usually given in millimeters. A gun can be considered as a particular kind of heat engine. In operation, the propellant charge located in the gun chamber is ignited by the primer. Gases produced by combustion of the propellant grains cause a rapid buildup of pressure. When a certain pressure is reached (shot-start pressure) which overcomes the forces of projectile weight and engraving of the projectile in the rifling, the projectile begins to move toward the muzzle which causes an increase in chamber volume. A maximum pressure is reached a few inches from the origin of rifling followed by a decrease in pressure all the way to the muzzle. At the muzzle, the pressure is 10 percent to 30 percent of the maximum pressure, depending on the geometry of the propellant grains. Artillery ammunition can be classified in many ways. Another classification is based on the manner in which the components are assembled for loading and firing. Complete rounds of artillery ammunition are known as either semi- fixed or separate loading. In contrast, small arms rounds are FIXED ammunition, with which it is not possible to adjust the amount of propellant in the cartridge case). Semi-fixed ammunition is characterized by an adjustable propelling charge. The propellant is divided into increments, or charges, and each increment of propellant is

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Page 1: Big Bullets for Beginners

Big Bullets for Beginners

Guns are generally classified according to use, size, and tradition. This varies among the military services. The basic distinction is between small arms and artillery. Any gun below a 20-millimeter bore size is generally classified as a small arm. The US Army distinguishes among mortars, howitzers, and guns. Mortars give high trajectories with short range and are usually loaded from the muzzle. Howitzers give medium-to-high trajectories, and guns provide flat-to-medium trajectories of longer range. Bore size is usually given in millimeters.

A gun can be considered as a particular kind of heat engine. In operation, the propellant charge located in the gun chamber is ignited by the primer. Gases produced by combustion of the propellant grains cause a rapid buildup of pressure. When a certain pressure is reached (shot-start pressure) which overcomes the forces of projectile weight and engraving of the projectile in the rifling, the projectile begins to move toward the muzzle which causes an increase in chamber volume. A maximum pressure is reached a few inches from the origin of rifling followed by a decrease in pressure all the way to the muzzle. At the muzzle, the pressure is 10 percent to 30 percent of the maximum pressure, depending on the geometry of the propellant grains.

Artillery ammunition can be classified in many ways. Another classification is based on the manner in which the components are assembled for loading and firing. Complete rounds of artillery ammunition are known as either semi-fixed or separate loading. In contrast, small arms rounds are FIXED ammunition, with which it is not possible to adjust the amount of propellant in the cartridge case).

Semi-fixed ammunition is characterized by an adjustable propelling charge. The propellant is divided into increments, or charges, and each increment of propellant is contained in a cloth bag. All of the cloth bags are held together by an acrylic cord, and are stored in the cartridge case. The primer is an integral part of the cartridge case, and is located on the base. Semi-fixed ammunition may be issued fuzed or unfuzed. Semi-fixed ammunition is used in 105mm howitzers. The ammunition is shipped in a wooden crate, with two fiber tubes in each crate. The fiber tubes are sealed at each end with tape. Upon removing the tape, the cannoneer will place the heavy end down first, and remove the projectile from the fiber tube. Next, the cartridge case is removed. Both the projectile and canister MUST REMAIN in their fiber cups until firing.

Separate loading ammunition has four separate components: primer, propellant, projectile, and fuze. The four components are issued separately. Upon preparation for firing, the projectile and propellant are loaded into the howitzer in two separate operations. Separate loading ammunition is used in 155mm howitzers.

There are two explosive trains in each conventional round of artillery ammunition; the PROPELLING CHARGE EXPLOSIVE TRAIN, and the PROJECTILE EXPLOSIVE TRAIN. The projectile reaches the target area by the power obtained from the propelling

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charge explosive train. The function of the projectile in the target area depends on the type of projectile explosive train.

The propelling charge explosive train consists of the primer, igniter, and propellant. The propelling charge explosive train is initiated by the primer, which is a small amount of very sensitive explosive. The primer is very sensitive to shock, friction, spark, and heat, and must be kept protected and away from other ammunition components. In separate loading ammunition, the primer is a separate item of issue. The igniter provides hot flaming gases and particles to ignite the propelling charge. The igniter consists of black powder or Clean Burning Igniter (CBI). The igniter is very hygroscopic and subject to rapid deterioration on absorption of moisture. If kept dry, however, it retains its explosive properties indefinitely. The igniter for semi-fixed ammunition is an integral part of the primer. It consists of a perforated tube filled with black powder and is permanently mounted in the cartridge case. In separate loading ammunition, the igniter is in a circular red pancake shaped bag sewn to the base increment of the propellant. When ignited by the primer, the igniter sends hot flaming gases around the charge to ignite the propellant.

A propellant is a large amount of insensitive but powerful explosive that propels the projectile to the target. Semi-fixed ammunition propellant is generally issued with seven increments numbered 1 through 7, and connected by a thin acrylic cord. Each increment is a different size because each increment has a different premeasured amount of propellant. Increment 1 and 2 are single perforated and increments 3-7 are multi-perforated. Separate loading ammunition propellants are issued as a separate unit of issue in sealed canisters to protect the propellant. The amount of propellant to be fired with artillery ammunition is varied by the number of propellant increments. The charge selected is based on the range to the target and the tactical situation.

“Smokeless powder” propellant is actually neither smokeless nor a powder. It is called smokeless to distinguish it from black powder, and it consists of grains of various shapes and sizes, up to an inch long, depending on the weapon for which they are intended. These grains are either of nitrocellulose (“single-based” powder) or a mixture of nitrocellulose and nitroglycerin (“double-based” powder). Nitrocellulose is created by soaking an organic cellulose product such as cotton or wood pulp in nitric acid. The resulting mixture is combined with chemical solvents, forming a doughy, pliable mass. This nitrocellulose is then extruded through a press into long cords, which are cut into grains of the appropriate size. The grains are then dried and the solvents removed for reuse.

Projectile Design

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Since the first projectile was manufactured, the demand for greater accuracy and greater range has influenced projectile design. Without specifically constructed shapes and exterior parts, there would be no standard ballistic characteristics for any group or type of projectiles. A lack of ballistic standardization would prevent the computation of firing tables. Modern projectiles are designed for maximum stability and minimum air resistance in flight.

Critical diameter is the smallest casing diameter that is needed to sustain a detonation. The critical diameter for an explosive is the minimum diameter mass of that explosive that can be detonated without being heavily confined. Two examples of these insensitive main charge explosives are PBXW-122 and PBXW-124. The composition of PBXW-122 by weight is 47% 3-nitro-1,2,4-triazol-5-one (NTO), 5% cyclotrimethylenetrinitramine (RDX), 20% ammonium perchlorate (AP), 15% aluminum, and 13% binder. PBXW-122 has a critical diameter of 7 inches. PBXW-122 has a sensitivity of 130K bars (ELSGT). The composition of PBXW-122 by weight is 27% NTO, 20% RDX, 20% aluminum, 20% ammonium perchlorate, and 13% binder. PBXW-122 has a critical diameter of between 3 and 4 inches. The composition of PBXN-110 by weight is 86% cyclotetramethylenetetranitramine (HMX) AND 14% Binder. PBXW-122 has a critical diameter of 7 inches, which means that it cannot be detonated in less than a 7 inch diameter mass unless heavily confined. Future underwater and bombfill explosives will have critical diameters greater than one inch.

Eyebolt Lifting Plugs and Fuze Well Plugs. A separate-loading projectile has an eyebolt lifting plug. Other types of projectiles have metal hex-head or plastic closing plugs. The plug is for lifting; to keep the fuze well clean, dry, and free of foreign matter; and to protect the fuze well threads. The plug is removed, and the appropriate fuze is inserted at the firing position. Some special-purpose semifixed projectiles are issued with the fuzes already assembled in the projectile.

Ogive. The ogive is the curved portion of a projectile between the fuze well and the bourrelet. It streamlines the forward portion of the projectile. The curve of the ogive usually is the arc of the circle, the center of which is located in a line perpendicular to the axis of the projectile and the radius of which is generally 6 to 11 calibers. The ogival head is that particular part of a projectile from the forward end of the section of even diameter to the point, or from the beginning of the forward slope to the point. The purpose of the ogival head is, that it offers less resistance to the air in the flight of the projectile than any other shaped head, and at the same time masses a sufficient amount of metal at the point to give desired penetration when it strikes.

Bourrelet. The bourrelet is an accurately machined surface that is slightly larger than the body and located immediately to the rear of the ogive. It centers the forward part of the projectile in the tube and bears on the lands of the tube. When the projectile travels through the bore, only the bourrelet and the rotating band of the projectile bear on the

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lands of the tube. It is at the forward end of the section of even diameter or cylinder of the projectile, and is of slightly enlarged diameter over that of the rest of the projectile. It serves the purpose of providing a bearing surface on the forward part of the projectile and enables its more accurate seating in the gun bore; also it concentrates the spinning or revolution about the long axis of the projectile.

Body. The body is the cylindrical portion of the projectile between the bourrelet and the rotating band. It is machined to a smaller diameter than the bourrelet to reduce the projectile surface in contact with the lands of the bore. The body contains most of the projectile filler.

Rotating Band. The rotating band is a cylindrical ring of comparatively soft metal that is pressed into a knurled, or roughened, groove near the base of the projectile. It mates with the forcing cone of the tube to eliminate gas wash (blow-by) and to provide forward obturation. The rotating band, in conjunction with the rifling of the tube, imparts spin to the moving projectile. A properly rammed separate-loading projectile is held in the tube at all angles of elevation by the wedging action of the rotating band against the forcing cone. The diameter of the band is equal to that of the base of the grooves of the rifling in the gun tube or bore. The function of the band is to give to the shell, as it travels down the gun bore, the rotation or rotary motion required and which is secured by the lands of rifling cutting into the soft copper band. Chips cut from the rotating band by the rifling fall into small grooves around the circumference of the band. The forward edge of the rotating band is beveled, or slanted down, so that the projectile will start easily and there will not be too much strain on the rifling. When the projectile is seated in the gun, the bevel of the rotating band rests into and matches the bevel on the lands of the rifling. When the projectile is traveling down the gun bore, the joint between the lands of the rifling and the rotating band forms an effectual gas-cheek to prevent any gases from getting around in front of the projectile.

Obturating Band. On some projectiles, there is a nylon obturating band below the rotating band to help in forward obturation. Two examples of 155-mm projectiles with this type of a band are the illuminating round and the high-explosive rocket-assisted round.

Base. The base is that portion of the projectile below the rotating band or obturating band. The most common type is known as the boattail base. This type of base streamlines the base of the projectile, gives added stability in flight, and minimizes deceleration by reducing the vacuum-forming eddy currents in the wake of the projectile as it passes through the atmosphere.

Base Cover. The base cover is a metal cover that is crimped, caulked or welded to the base of the projectile. It prevents hot gases of the propelling charge from coming in contact with the explosive filler of the projectile through possible flaws in the metal of the base.

 

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Projectile Design

Since the first projectile was manufactured, the demand for greater accuracy and greater range has influenced projectile design. Without specifically constructed shapes and exterior parts, there would be no standard ballistic characteristics for any group or type of projectiles. A lack of ballistic standardization would prevent the computation of firing tables. Modern

projectiles are designed for maximum stability and minimum air resistance in flight.

Critical diameter is the smallest casing diameter that is needed to sustain a detonation. The critical diameter for an explosive is the minimum diameter mass of that explosive that can be detonated without being heavily confined. Two examples of these insensitive main charge explosives are PBXW-122 and PBXW-124. The composition of PBXW-122 by weight is 47% 3-nitro-1,2,4-triazol-5-one (NTO), 5% cyclotrimethylenetrinitramine (RDX), 20% ammonium perchlorate (AP), 15% aluminum, and 13% binder. PBXW-122 has a critical diameter of 7 inches. PBXW-122 has a sensitivity of 130K bars (ELSGT). The composition of PBXW-122 by weight is 27% NTO, 20% RDX, 20% aluminum, 20% ammonium perchlorate, and 13% binder. PBXW-122 has a critical diameter of between 3 and 4 inches. The composition of PBXN-110 by weight is 86% cyclotetramethylenetetranitramine (HMX) AND 14% Binder. PBXW-122 has a critical diameter of 7 inches, which means that it cannot be detonated in less than a 7 inch diameter mass unless heavily confined. Future underwater and bombfill explosives will have critical diameters greater than one inch.

Eyebolt Lifting Plugs and Fuze Well Plugs. A separate-loading projectile has an eyebolt lifting plug. Other types of projectiles have metal hex-head or plastic closing plugs. The plug is for lifting; to keep the fuze well clean, dry, and free of foreign matter; and to protect the fuze well threads. The plug is removed, and the appropriate fuze is inserted at the firing position. Some special-purpose semifixed projectiles are issued with the fuzes already assembled in the projectile.

Ogive. The ogive is the curved portion of a projectile between the fuze well and the bourrelet. It streamlines the forward portion of the projectile. The curve of the ogive usually is the arc of the circle, the center of which is located in a line perpendicular to the axis of the projectile and the radius of which is generally 6 to 11 calibers. The ogival head is that particular part of a projectile from the forward end of the section of even diameter to the point, or from the beginning of the forward slope to the point. The purpose of the ogival head is, that it offers less resistance to the air in the flight of the projectile than any other shaped head, and at the same time masses a sufficient amount of metal at the point to give desired penetration when it strikes.

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Bourrelet. The bourrelet is an accurately machined surface that is slightly larger than the body and located immediately to the rear of the ogive. It centers the forward part of the projectile in the tube and bears on the lands of the tube. When the projectile travels through the bore, only the bourrelet and the rotating band of the projectile bear on the lands of the tube. It is at the forward end of the section of even diameter or cylinder of the projectile, and is of slightly enlarged diameter over that of the rest of the projectile. It serves the purpose of providing a bearing surface on the forward part of the projectile and enables its more accurate seating in the gun bore; also it concentrates the spinning or revolution about the long axis of the projectile.

Body. The body is the cylindrical portion of the projectile between the bourrelet and the rotating band. It is machined to a smaller diameter than the bourrelet to reduce the projectile surface in contact with the lands of the bore. The body contains most of the projectile filler.

Rotating Band. The rotating band is a cylindrical ring of comparatively soft metal that is pressed into a knurled, or roughened, groove near the base of the projectile. It mates with the forcing cone of the tube to eliminate gas wash (blow-by) and to provide forward obturation. The rotating band, in conjunction with the rifling of the tube, imparts spin to the moving projectile. A properly rammed separate-loading projectile is held in the tube at all angles of elevation by the wedging action of the rotating band against the forcing cone. The diameter of the band is equal to that of the base of the grooves of the rifling in the gun tube or bore. The function of the band is to give to the shell, as it travels down the gun bore, the rotation or rotary motion required and which is secured by the lands of rifling cutting into the soft copper band. Chips cut from the rotating band by the rifling fall into small grooves around the circumference of the band. The forward edge of the rotating band is beveled, or slanted down, so that the projectile will start easily and there will not be too much strain on the rifling. When the projectile is seated in the gun, the bevel of the rotating band rests into and matches the bevel on the lands of the rifling. When the projectile is traveling down the gun bore, the joint between the lands of the rifling and the rotating band forms an effectual gas-cheek to prevent any gases from getting around in front of the projectile.

Obturating Band. On some projectiles, there is a nylon obturating band below the rotating band to help in forward obturation. Two examples of 155-mm projectiles with this type of a band are the illuminating round and the high-explosive rocket-assisted round.

Base. The base is that portion of the projectile below the rotating band or obturating band. The most common type is known as the boattail base. This type of base streamlines the base of the projectile, gives added stability in flight, and minimizes deceleration by reducing the vacuum-forming eddy currents in the wake of the projectile as it passes through the atmosphere.

Base Cover. The base cover is a metal cover that is crimped, caulked or welded to the base of the projectile. It prevents hot gases of the propelling charge from coming in

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contact with the explosive filler of the projectile through possible flaws in the metal of the base.

 Large Caliber Ammunition - Types of Projectiles

A projectile or shell is a missle fired from the muzzle of a gun; it is always the projectile, whether issuing from the muzzle of a Breech-Loading Rifle, using separate ammunition, or from the muzzle of a Rapid-Fire Gun, using fixed, cartridge-case ammunition. Projectiles for guns of and above seven inches in caliber are called major-caliber projectiles. For guns of six-inch caliber and smaller they are called minor-caliber projectiles. The principal function of the projectile is to carry its charge intact to the enemy's most vulnerable point, and its relative efficiency will be in a measure proportional to its carrying capacity. The first projectiles used were stones thrown from slings (afterwards lead bullets were projected in the same way), arrows from the long bow, and darts andjavelins thrown by hand. In the sieges of walled towns, in very early days, ballista, and catapults were used as a species of heavy ordnance, the former to hurl large stones, and the latter, wooden beams shod with iron and often covered with inflammable material. The projectile, as it is understood in modern times, came in with the use of gunpowder in warfare, and developed with the improvements in weapons using it. While lead answered all the purposes in small-arms, it was found too soft for battering with larger guns, and stone shot being not only too light for good flight, but also deficient in tenacity, early gave way to iron.

Projectiles can be broadly classified according to three main types: spin-stabilized, fin-stabilized, and rocket assisted (both fin- and spin-stabilized). Formal military classification is based on the intended use of the projectile and the composition of the explosive charge (i.e., antipersonnel, antitank, and incendiary). Some very significant progress in projectile design has been made in the past few years. The form of all projectiles is approximately the same, namely, that of a hollow steel cylindrical case with pointed head, having a soft metal band near the base which takes the rifling of the gun and gives the projectile the twisting motion which keeps it steady during flight.

SPIN-STABILIZED PROJECTILES Most guns in use today use spin-stabilized projectiles. Spinning a projectile promotes flight stability. Spinning is obtained by firing the projectiles through a rifled tube. The projectile engages the rifling by means of a rotating band normally made of copper. The rotating band is engaged by the lands and grooves. At a nominal muzzle velocity of 2800 feet per second, spin rates on the order of 250 revolutions per second are encountered. Spin-stabilized projectiles are full bore

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(flush with the bore walls) and are limited approximately to a 5:1 length-to-diameter ratio. They perform very well at relatively low trajectories (less than 45° quadrant elevation). In high trajectory applications they tend to overstabilize (maintain the angle at which they were fired) and, therefore, do not follow the trajectory satisfactorily.

FIN-STABILIZED PROJECTILES These projectiles obtain stability through the use of fins located at the aft end of the projectile. Normally, four to six fins are employed. Additional stability is obtained by imparting some spin (approximately 20 revolutions/second) to the projectile by canting the leading edge of the fins. Fin-stabilized projectiles are very often subcaliber. A sabot, wood or metal fitted around the projectile, is used to center the projectile in the bore and provide a gas seal. Such projectiles vary from 10:1 to 15:1 in length-to-diameter ratio. Fin-stabilized projectiles are advantageous because they follow the trajectory very well at high-launch angles, and they can be designed with very low drag thereby increasing range and/or terminal velocity. However, fin-stabilized projectiles are disadvantageous because the extra length of the projectile must be accommodated and the payload volume is comparatively low in relation to the projectile length.

In contrast to conventional spin-stabilized projectiles which derive their in-flight stability from the gyroscopic forces resulting from the high rate of spin, the finned projectiles are stabilized during flight by aerodynamic forces acting on the projectile. Although projectile spin does not contribute to the stabilization of finned projectiles, a low rate of roll around the longitudinal axis is desired to minimize the adverse effects of mass and configurational asymmetries which may result from material imperfections and from manufacturing tolerances.

Fin-stabilized projectiles are ideally launched from smooth bore guns which, due to the absence of rifling, do not impart a rolling motion. Such weapons are installed, for instance, on advanced battle tanks and commonly have calibers of 60 millimeters or more.

Automatic cannons having calibers ranging approximately from 12.7 to 40 millimeters have almost exclusively rifled barrels and generally fire various types of spin-stabilized projectiles, including armor-piercing projectiles. In order to improve the armor penetration of such weapons, it is desirable to develop technology permitting successful employment from rifled gun barrels of fin-stabilized armor-piercing projectiles with their inherent high degree of terminal effectiveness. In this case, successful employment means compatibility of the ammunition with the gun and feeder system, which in turn requires the necessary structural integrity to function reliably under all operating conditions specified for such weapons while at the same time providing a projectile accuracy which is equal to or better than that of spin-stabilized projectiles fired from the same weapon.

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Commonly, fin-stabilized projectiles consist of a subcaliber penetrator and a fin assembly of four or more fins attached to the rear of the penetrator. The projectile assembly is symmetric to its longitudinal axis and is fired from the gun by means of a discarding sabot. Two important functions of the discarding sabot are to support and guide the subcaliber projectile along the centerline of the gun barrel during acceleration and to form a seal to contain the propellant gasses during travel in the barrel. The latter function is accomplished by the rotating band which engages the rifling grooves of the gun barrel and in doing so imparts spin to the projectile commensurate with the rifling twist of the barrel and the projectile muzzle velocity.

Fin-stabilized projectiles reflecting the current state of the art incorporate a sliding seat between the rotating band and the sabot body. The sliding seat is designed such as to reduce by approximately 70 to 90 percent the amount of spin transmitted from the rotating band, which picks up the full spin, to the sabot body. The degree of spin transmission within the seat of the rotating band is determined by sliding friction. Thus, upon exit from the muzzle of the gun the fin-stabilized projectile has a rate of spin equal to approximately 10 to 30 percent of that of a spin-stabilized projectile launched at the same muzzle velocity.

There are two problem areas encountered with this method of firing fin-stabilized projectiles from a rifled cannon. Firstly, it is difficult to control the spin reduction in the sliding seat with a degree of repeatability necessary to assure acceptable projectile accuracy over the entire range of operating conditions specified for military employment. Variations in projectile temperature from -40.degree. to +60.degree. C., changes in humidity, finite manufacturing tolerances, contamination by dust, salt and other substances entering between the rotating band and its seat, etc., influence the friction coefficient in the band seat and with it the degree of spin transmission.

Secondly, centrifugal forces acting on sabot components are very effective in initiating the instantaneous and symmetric separation of the sabot from the penetrator upon exit from the muzzle of the gun. With reduced projectile spin the centrifugal forces acting on the sabot components are reduced by the square of the spin ratio. As a result, the sabot separation is neither as rapid nor as precise as with a nonslipping rotating band and is increasingly more dependent on aerodynamic forces.

The access of aerodynamic forces to the projectile is delayed by the efflux of high velocity propellant gasses upon exit of the projectile from the muzzle of the gun. These propellant gasses envelop the projectile temporarily in a reverse flow field. Only upon entering into the ambient air, which occurs at a range of approximately 30 calibers from the muzzle, do the aerodynamic forces become fully effective in sabot separation. The magnitude of the aerodynamic forces prevailing for sabot separation is only a fraction of the centrifugal forces available when launching at full spin and therefore a considerably more fragile sabot construction is required to assure its fracture and separation. In addition, because of size limitations of ammunition of calibers up to 40 millimeters, the physical dimensions of sliding rotating bands, inclusive of their seats, are small, thus resulting in rather delicate and vulnerable components. In contrast, utilization of a

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nonslipping rotating band allows for the use of a stronger sabot which is advantageous when employed from high rate of fire cannons and their correspondingly high structural loads during feeding and ramming.

Fin-stabilized projectiles equipped with discarding sabots incorporating slipping rotating bands experience considerable variations in spin rate at exit from the muzzle due to deviations in the friction coefficient within the sliding seat of the band. As a result the subsequent acceleration or deceleration of the projectile spin may result in conditions where the spin rate is equal to the nutation frequency of the projectile and resonance instability will occur. The lower projectile spin rate at muzzle exit and consequent reduction in centrifugal forces acting on the sabot decrease the rapidity and symmetry of the discard of the sabot components and therewith result in increased projectile dispersion.

SABOT A sabot is a lightweight carrier used both to position a missile or subcaliber projectile inside a gun tube and to transmit energy from the propellant to the projectile. The sabot works much like a person throwing a dart, where the thrower's arm movement acts as both the propellant-driving gas and the sabot's energy-gathering pusher.

In general, guns operate with a fixed mass to be propelled out of the gun's tube. The sabot is necessary to transfer propellant energy but is a parasitic weight in terms of projectile target performance. Reducing the sabot's weight allows greater projectile velocity. The weapons thus penetrate deeper, with more lethal results. But materials used to fabricate sabots can only be as lightweight as they are strong enough to withstand great pressures and loads during gun-tube acceleration.

Three types of armor piercing projectiles are currently utilized in small caliber gun systems. One of the designs is of a conventional projectile shape and is full-bore diameter, consisting of a combination of high strength steel or high density material as a penetrator swaged or inserted into a suitable jacket or sleeve material. At the projectile base is an opening for a tracer cavity of adequate depth and diameter to provide a clear visual trace of the entire projectile trajectory. This type of full-bore projectile utilizes the high density or high strength penetrator and to some extent the jacket or sleeve material and its geometry to affect armor penetration. This type of projectile has severely limited armor penetration capability at target engagement ranges beyond several hundred meters, due to its high drag configuration.

It has been demonstrated that sub-caliber high density rod type penetrators are capable of penetrating significantly more armor than the full-bore projectiles at target ranges beyond several hundred meters. This is due to the high density rod's more efficient armor penetration geometry and the greater mass per cross sectional area of the sub-caliber rod flight projectile, which results in it losing less velocity from aerodynamic drag. To take advantage of the rod's high ballistic coefficient and to provide increased initial launch velocities, sabots were designed to encapsulate the rod penetrator during handling, storage, and gun firing, and to discard shortly after exiting the muzzle, thus allowing only the rod penetrator to continue in flight toward the target. One type of discarding sabot

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projectile has been demonstrated in small caliber guns to provide increased armor penetration over full-bore projectiles. This is the Armor Piercing Discarding Sabot (APDS) projectile, which utilizes a spin stabilized sub-caliber penetrating core as the flight projectile. APDS projectiles using high density rod penetrators have been developed for guns from caliber 5.56 millimeter through caliber 120 millimeter. Given aerodynamic considerations, APDS projectile designs below caliber 25 millimeter do not allow the inclusion of a tracer cavity without degrading penetrator performance. The tracer cavity in these projectiles significantly reduces the available high density rod material required for armor penetration.

It has been demonstrated that armor piercing fin stabilized discarding sabot (APFSDS) projectiles penetrate more armor at greater ranges than spin stabilized APDS projectiles, due to the longer allowable penetrator lengths that can be launched and flown to the target with accuracy and stability. APFSDS projectiles utilizing high density sub-caliber rod penetrators have been developed for both rifled barrel and smooth bore guns from caliber 25 millimeter through 140 millimeter, and these designs have permitted the incorporation of an adequate tracer cavity in the rear of the flight projectile without degradation of the rod's armor penetration performance.

Prior art delay discarding sabot projectiles has typically taken the form of a metal pusher having a forward facing recess surrounding a high density metal penetrator, both pusher and penetrator typically being right circular cylindrically shaped members. The prior art pusher typically had a pyrotechnic delay column and expulsion charge adapted to explode after the assembled pusher/penetrator has been ejected from the gun barrel so as to axially separate the penetrator from the pusher. The inherent problem with the prior art configuration was that there could, because of normal machining/manufacturing variations, be significant differences in dimensions between the outer diameter of the penetrator and the inner diameter of the aforesaid recess. The difference in dimensions vary from round to round and hence result in a substantial variation of release forces, i.e., the forces tending to hold the penetrator within the pusher. This uncontrollable variation in release force accordingly would dramatically and significantly change the separation point from one round of ammunition to another, greatly reducing the overall accuracy, i.e., failing to produce a projectile having a low dispersion factor.

Previously, the lightest weight sabots were made of aluminum. In the past, the search for lighter weight sabot materials focused on metal composites. But researchers were continually frustrated by failure-metal composites simply were too brittle. Attention then shifted toward polymer-based composites, which were being used extensively in thin structures for aerospace applications. Researchers began to consider fiber composites for complex shaped structures that needed to survive multidirectional stresses. Some engineers refer whimsically to a fiber composite as "string and glue." It consists of high-strength carbon fibers, which must be laid down and oriented to yield maximal strength and handle maximal stress. Polymer is used to glue together layers of these fibers in a process similar to that used to manufacture plywood. When layers are glued together, the grains of adjacent layers are arranged either at right angles or at some wide angle to each other. Once a piece of the material has been fabricated, it can be machined into the

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required form. Fairly thick pieces that can withstand high three-dimensional stress are used for sabot material.

Long rod penetrators are well known and are adapted to penetrate armor. Long rod penetrators have stabilizing fins which are either welded to the penetrator rod or threadably fixed to the penetrator rod. Such stabilizing fins are necessary to guide the penetrator in true flight to the target. In conventional long rod penetrators, if armor is thick enough, it is possible that the long rod remains unpenetrated if the fins remain at least partly locked to the penetrator or are only partly sheared from the penetrator as the penetrator moves through the armor.

It would, of course, be desirable to reduce the retardation effect of the fins which may prevent the penetrator from moving as far through the armor as possible. This problem is intensified when using stronger ferrous type materials for the guide fins and penetrator rod to accommodate new propellants which expose the assembly to higher temperatures. Thus, armor is constantly being improved in toughness, hardness, obliquity and is being constructed in multilayer fashion. All of these changes require improvements in penetrators by increasing penetrating power and range. Such improvements are accomplished by adjustment of the length to the diameter ratio of the penetrator, the use of new material such as tungsten and depleted uranium, the use of new propellants, new sabots and new stabilizing fin structures and materials, therefore, and the like. The new propellants require the penetrator to withstand higher temperature in the gun tube since the rod and the guide fins are heated to higher temperatures. Consequently, stabilizing fins which conventionally were made from aluminum alloys are now being made of ferrous alloys which have much higher strength and are capable of withstanding higher temperatures.

When using aluminum alloys, the fins tended to shear readily from the penetrator body when the fins reached the surface of the armor being penetrated and did not produce a substantial retardation force against continued movement of the penetrator rod into their armor. However, higher strength stabilizing fins do not shear until a considerably higher force is applied between the rod body and the fin so that a substantial retardation force is present as the penetrator shaft enters the armor and the fins encounter the armor surface. In other words, a portion of the energy which propels the rod into the armor will be used up by "dragging" the fins through the rod cavity in the armor or in shearing or tearing the fin from the rod. As a result, the full impact energy of the rod is not used in accomplishing its primary objective of passing through a given armor thickness.

ROCKET-ASSISTED PROJECTILES There are two main reasons for developing rocket-assisted projectiles: (1) to extend the range over standard gun systems, and (2) to allow for lighter mount and barrel design and reduce excessive muzzle flash and smoke by reducing the recoil and setback forces of standard gun systems. Since the ranges are different, the above two objectives represent opposite approaches in the development of rocket-assisted projectiles. Normally, one or the other establishes the performance of the rocket-assisted projectile under development although some compromise in the two approaches may be established by the design objectives.

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Large Caliber Ammunition - Types of Warhead

One basic classification of types of warheads or projectiles differentiates between shells that are hollow pieces of metal containing a filler charge of some sort, and shot, which are solid pieces of metal. For convenience of discussion, large caliber ammunition may be be classified into five major groups: blast (including air and underwater burst), fragmentation, shaped charge, pyrotechnics, and cluster. The basic function of any weapon is to deliver a destructive force on an enemy target. High explosive warheads cause damage by concussion (blast effects) or by penetration of high-energy fragments. In general, there are three types of high explosive warheads that employ the latter method to accelerate metal fragments generally including (1) directed energy warheads, (2) fragmentation warheads, and (3) continuous-rod warheads (CRW). Shaped Charge

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Warheads refers to Shaped Charge Warheads and Explosively Formed (a.k.a. forged) Penetrators (EFPs) that are directed in that the high explosive energy is focused on a liner, which is typically made of metal. These warheads consist of a hollow liner of thin metal material backed on the convex side by explosive. Upon detonation, a detonation wave sweeps forward and hydrodynamically collapses the liner (in the case of a shaped charge) or deforms the liner (in the case of EFPs) along its axis of symmetry forming a directed jet or EFP which penetrates a localized area on a target of interest. The Shaped Charge effects concept can be used in multiples, where metal liners/projectiles are distributed, around the circumference of a high explosive charge. In this case, the detonation does not collapse a liner along its linear axis of symmetry, rather, the detonation wave hits the liners perpendicularly (almost symmetrically to the axis of the liners). High explosive fragmentation warheads constitute one of the most widely used warhead approaches in all types of ammunition. Fragmentation warheads are intended to defeat virtually all types of targets, excluding overburden targets underground and underwater, and heavily armored targets. In fragmentation warheads, the detonation of the secondary high explosive core generates a large amount of heat and gaseous products. High explosives have an extremely high rate of reaction and the presence of a detonation (shock) wave that moves faster than the speed of sound in the explosive material. Upon detonation, the metal warhead casing almost instantaneously catastrophically fails and bursts, producing a blast of rapidly expanding hot gases and casing fragments. The rapidly expanding gasses will compress the surrounding air and create a shock wave which propagates outwards at near the speed of sound in air (.about.340 m/s). The energy of the fragments dissipate more slowly than the energy of a shock wave and, thus, fragments tend to be lethal to a greater range than the blast effects for hard targets. As a function of design, fragments from a fragmenting warhead have various distribution patterns and lethality characteristics. The fragment distribution pattern is a function of the amount and nature of the explosive material (i.e. how energetic the explosion is), the mass of the fragmenting material, the fragmentation size, and the configuration (geometry, initiation scheme) of the warhead. For example, the detonation of a bomb projects the fragments in an approximate cylindrical pattern and a hand-grenade projects fragments in an approximate spherical pattern. Uncontrolled fragmentation patterns, such as those used in general-purpose bombs, occur by the natural break up of the outer casing occurring from the detonation of the surrounding explosive charge. This event forms fragments of random size and lethality. Manipulating the fragment formation process can more predictably control fragmentation patterns and fragment uniformity. Controlled fragment formation can be accomplished in several ways including: designing pre-scored failure regions (grid patterns) on the outer/inner casing or outer surface of the explosive; sandwiching an intermediate mesh material between the outer casing and the explosive core; and, arranging preformed fragments around the main charge explosive such as spheres or cubes. By controlling the fragment formation process, the relative size and, therefore, the optimized bulk fragment distribution pattern over an area is constrained to maximize the defeat probability/lethality against an anticipated target set of known thickness, obliquity, and material properties. Continuous-Rod Warhead (CRW) CRW technology incorporates two overlapping layers of ductile rods that are oriented around the circumference running parallel along the length of an explosive core. The rods are alternately connected together, end-to-end, by a weld (in a zigzag/accordion pleat

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fashion). Upon detonation, the continuous-rod payload rapidly expands radially outward, bending or "unfolding" the welded ends to form a ring of interconnected rods. A ring of interconnected rods is produced about the axis of the weapon. The ring expands from a highly compressed zigzag pattern to an expanded, almost flat, zigzag pattern using an expansion mechanism similar to a half-plane pantograph. During this expansion, the explosive energy is focused in a single plane such that when the rods strike a target, damage is produced by a cutting action giving it the nickname "flying buzzsaw". The metal density of a normal fragmentation warhead attenuates inversely with the square of the distance (1/R.sup.2). However, because it is non-isotropic, the metal density of a continuous-rod payload attenuates inversely as the distance from the point of detonation (1/R). To ensure that the rods stay connected at detonation, the maximum initial rod velocity is limited to the range of 1050 to 1150 meters per second. The initial fragment velocities of fragmentation warheads are in the range of 1800 to 2100 meters per second. Thus, in comparison, CRWs cannot produce as much destructive energy potential as fragmentation warheads. However, the distribution pattern is highly focused, and the rods are interconnected, to increase the relative mass interacting with a target in a highly localized area. Only one invention uses discrete rods in a fragmentation type of warhead and it closely mimics the physical architecture of the CRW (layers of rods that are oriented around the circumference and run parallel and along the length of an explosive core), but without physical interconnections being established between adjacent rods. U.S. Pat. No. 4,216,720 entitled Rod-fragment controlled-motion warhead (RFCMW) discloses destructive fragments used in a warhead that are in the form of discrete tapered rods that are substantially the same length as the cylindrical warhead itself and are placed vertically around and parallel to the axis of the warhead. The warhead system is designed to dynamically rotate the rods to form the expansion and kill radius/mechanism. U.S. Pat. No. 4,216,720 points to some deficiencies of the RFCMW concept as follows: the pattern of these rod-type fragments has been of such a discontinuous nature to results in a high likelihood of missing targets; and, the rods tend to spread in the axial direction, rather than being driven radially. Another major shortfall of the RFCMW concept is that a high explosive detonation event is used to form the geometric orientation of the rods through a dynamically controlled rotation of each discrete rod to provide the expansion mechanism. The propelling motion is empirically derived for each configuration and optimized to a 90 degree rotation for each discrete rod. If the collective interrelated system of discrete rods under or over rotates, the effective continuous coverage (end-to-end) radius is reduced. Additionally, the propellering motion of each rod within the RFCMW must have the same angular velocity (and acceleration rate) to ensure the discrete rods do not rotate into each other. The propellering motion of the discrete taper rods requires a perfectly balance rod after that rod has experience some degree of deformation following the explosive detonation of the explosive core. The detonation of the explosive charge will most likely cause spalling and material deformation of the tapered rods, which will randomly change their aerodynamic characteristics while unpredictably shifting the center-of-balance and, thus, introducing random discontinuities in the propellering motion of each discrete rod. If a single rod does not perform as designed or if one discrete rod prematurely encounters an obstacle (such as topography, a tree, etc.) before reaching the target, its rotation will be significantly altered and cause a domino effect whereby the interrelated discrete rods tumble into each other and consume the effective warhead

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energy. A further major shortfall in the RFCMW is the aerodynamic stability of this concept whereby the end effect must be achieved by a highly controlled formation pattern that is achieved by dynamic, balanced rotation that is highly intolerant of drift, asymmetries, and induce asymmetries such as spalling and material deformation following the warhead detonation. Time sequencing of six degrees-of-freedom motion must be achieved to propel the discrete rods radially outward, while they are simultaneously and dynamically rotating about their respective precise center axes. This requires that each discrete rod rotates at the same angular rate while experiencing a uniform velocity ratio (uniform velocity to mass ratio) during and after an explosive event across the entire length of the discrete rod which has an unusually high aspect ratio (the claimed length-to-diameter ratio is 28:1) so that all portions are subjected to both the same an outward and angular velocity to arrive at an end-to-end disposition. Other shortfalls of the RFCMW concept are as follows: the tapered rods will reduce the penetration capability at the thinned portion of the rods and therefore reduce the damage level to the intended target; and, it is doubtful that the warhead is relatively inexpensive as claimed--the warhead would be relatively expensive due to the understanding that the RFCMW requires relatively high control of rod material properties, highly toleranced machined metal parts, manufactured parts, and fabricated assemblies, and a potentially complex explosive initiation system to ensure effective results (also true for a CRW). Therefore, it is desired to provide a radially expanding kill effect similar to the CRW by using geometrically prearranged segmented circular rods placed horizontally (perpendicular to the warhead axis) around a cylindrical warhead to produce a geometrically coupled, helical spirally ring of interrelated and adjacent segmented circular rods upon detonation of the explosive core, to increase the effective mass on the target within a localized region, to create multiple impact sites within a projected height, to create lethality at and somewhat beyond the full expansion diameter of the warhead, and to create unique target defeat mechanisms compared to that of the CRW or that of all known prearranged fragmentation warheads. The Segmented Rod Warhead (SRW) is a high explosive warhead designed to radially project mechanically and geometrically prearranged fragments, in the form of multiple layers of discrete and helically wound circular segmented rods, in a prescribed, highly controlled, parallel path and radial distribution, such that at full expansion, the adjacent, individual rods align themselves end-to-end in a helical, stair-step fashion to form a continuous spiral to defeat a target, rather than pepper a target with a distribution of fragments. The expansion mechanism is radial, meaning the height of the warhead cylinder dictates the cylindrical height of the kill region. The radius at full expansion is mathematically derived from the diameter of the packaged warhead and the arc length of the discrete circular rod segments. The SRW focuses the available warhead energy on a localized area of a target in a non-isotropic fashion. This cumulative and synergistic effect greatly weakens a target by the concentration and interaction of mechanically arranged adjacent rod segments within the same localized failure region as compared to a wide spread distribution of fragments over a target of interest.

Blast

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A blast warhead is one that is designed to achieve target damage primarily from blast effect. When a high explosive detonates, it is converted almost instantly into a gas at very high pressure and temperature. Under the pressure of the gases thus generated, the weapon case expands and breaks into fragments. The air surrounding the casing is compressed and a shock (blast) wave is transmitted into it. Typical initial values for a high-explosive weapon are 200 kilobars of pressure (1 bar = 1 atmosphere) and 5,000 degrees celsius.

The energetic materials used by Department of Defense munitions produce an exothermic reaction defined either as a deflagration or a detonation. A deflagration is an exothermic reaction that propagates from the burning gases to the unreacted material by conduction, convection, and radiation. In this process, the combustion zone progresses through the material at a rate that is less than the velocity of sound in the unreacted material.

In contrast, a detonation is an exothermic reaction that is characterized by the presence of a shock wave in the material that establishes and maintains the reaction. A distinctive difference is that the reaction zone propagates at a rate greater than sound velocity in the unreacted material. Every material capable of detonating has a characteristic velocity that is under fixed conditions of composition, temperature, and density.

The violent release of energy from a detonation in a gaseous medium gives a sudden pressure increase in that medium. The pressure disturbance, termed the blast wave, is characterized by an almost instantaneous rise from the ambient pressure to a peak incident pressure (Pso). This pressure increase, or shock front, travels radially from the burst point with a diminishing velocity that always is in excess of the sonic velocity of the medium. Gas molecules making up the front move at lower velocities. This latter particle velocity is associated with a "dynamic pressure," or the pressure formed by the winds produced by the shock front.

As the shock front expands into increasingly larger volumes of the medium, the peak incident pressure at the front decreases and the duration of the pressure increases. If the shock wave impinges on a rigid surface oriented at an angle to the direction of propagation of the wave, a reflected pressure is instantly developed on the surface and the pressure is raised to a value that exceeds the incident pressure. The reflected pressure is a function of the pressure in the incident wave and the angle formed between the rigid surface and the plane of the shock front.

When an explosion occurs within a structure, the peak pressure associated with the initial shock front will be extremely high and, in turn, will be amplified by reflections within the structure. In addition, the accumulation of gases from the explosion will exert additional pressures and increase the load duration within the structure. The combined effects of both pressures eventually may destroy the structure if it is not strengthened sufficiently or adequate venting for the gas and the shock pressure is not provided, or both. For structures that have one or more strengthened walls, venting for relief of excessive gas or shock pressures, or both, may be provided by means of openings in or frangible construction of the remaining walls or roof, or both. This type of construction will permit

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the blast wave from an internal explosion to spill over onto the exterior ground surface. These pressures, referred to as exterior or leakage pressures, once released from their confinement, expand radially and act on structures or persons, or both, on the other side of the barrier.

Conventional structures are designed to withstand roof snow loads of 30 pounds per square foot (1.44 kilopascals) and wind loads of 100 miles per hour (161 kilometers per hour). The loads equate to 0.2 pounds per square inch (psi).

Fragmentation Warhead

Common usage distinguishes between a gunshot wound and a shrapnel wound. More precise usage would term the later a fragment wound. Strictly defined, shrapnel means preformed fragments (the fragments exist already made within the explosive munition). Thus, fragmenrs from a random-fragmentation shell are not shrapnel. Also note that by strict definition, flechettes are shrapnel.

Naturally fragmenting warheads are primarily implemented in gun projectiles, mortar rounds and small rockets. These warheads are generally a compromise between cost and warhead case fragmentation performance. Although naturally fragmenting warheads are generally the least expensive method of high-volume warhead production, they usually do not fragment into the optimum fragment size for their given application or target set. For example, the target set for most gun-fired projectiles and mortar rounds includes personnel and other "light" targets such as trucks. Such applications generally require an optimum fragment size of approximately 15-30 grains. This fragment size is difficult to consistently achieve with naturally fragmenting warheads. Specifically, fragments are often too large which results in inefficient warhead performance.

A blast fragmentation type warhead is designed to destroy enemy missiles, aircraft, re-entry vehicles, and other targets. When the missile carrying the warhead reaches a position close to an enemy missile or other target, a pre-scored or pre-made band of metal on the warhead is detonated and pieces of metal are accelerated with high velocity and strike the target. The fragments of the blast fragmentation type warhead, however, are not always effective at destroying the target and biological bomblets and/or chemical submunition payloads can survive and still cause heavy casualties.

An important consideration in the analysis of explosions is the effect of the fragments generated by the explosion. These fragments are known as primary or secondary fragments depending on their origin. Primary fragments are formed as a result of the shattering of the casing of conventional munitions. These fragments usually are small in size and travel initially at velocities of the order of thousands of feet per second. Secondary fragments are formed as a result of high blast pressures on structural components and items in close proximity to the explosion. These fragments are somewhat larger in size than primary fragments and travel initially at velocities in the order of hundreds of feet per second. A hazardous fragment is one having an impact energy of 58 ft-lb (79 joules) or greater.

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The study of ballistics, the science of the motion of projectiles, has contributed significantly to the design of fragmentation warheads. Specifically, terminal ballistics studies attempt to determine the laws and conditions governing the velocity and distribution of fragments, the sizes and shapes that result from bursting different containers, and the damage aspects of the bursting charge fragmentation.

Approximately 30% of the energy released by the explosive detonation is used to fragment the case and impart kinetic energy to the fragments. The balance of available energy is used to create a shock front and blast effects. The fragments are propelled at high velocity, and after a short distance they overtake and pass through the shock wave. The rate at which the velocity of the shock front accompanying the blast decreases is generally much greater than the decrease in velocity of fragments, which occurs due to air friction. Therefore, the advance of the shock front lags behind that of the fragments. The radius of effective fragment damage, although target dependent, thus exceeds consid-erably the radius of effective blast damage in an air burst.

Whereas the effects of an idealized blast payload are attenuated by a factor roughly equal to 1/R3 (R is measured from the origin), the attenuation of idealized fragmentation effects will vary as 1/R2 and 1/R, depending upon the specific design of the payload. Herein lies the principle advantage of a fragmentation payload: it can afford a greater miss distance and still remain effective because its attenuation is less.

Conventional bombs and warheads detonate in a manner that produces fragments of irregular size and shape. Fragments of nearly identical shape will disperse in a predictable pattern based on their orientation in the warhead and the configuration and method of detonation of the explosive charge in the warhead. Prior to construction of the warhead, the size and shape of the fragments must be determined, based on the desired warhead size and the object target - using standard techniques for determination of required kinetic energy for defeating the target and kinetic energy to be available in the fragment from the mass of fragment and explosive charge to be used.

Framentation warheads generally involve scoring or otherwise weakening the warhead casing, thus allowing a preferentail rupture at the weakened area and thereby causing some amount of blast concentration in the vicinity proximate to the weakened area of the casing. On detonation of the charge, shock waves strike the shell at differential increments of time, causing preferential fragmentation in the resulting shell burst. Configurations typically involve a single explosive burster charge surrounded by fragments, but because of low coupling efficiencies, a considerable amount of explosive was required if desirably high fragment velocities were to be achieved with a limited number of fragments.

To avoid random distribution of fragments propelled by exploding anti-property and personnel devices, it is necessary to control the size, shape, and weight of the fragments. Small fragments have low mass and will not possess optimum amount of kinetic energy against a desired target compared to a larger mass fragment traveling at the same velocity. Large fragments, and in particular, bar, plate, and diamond shapes, however,

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offer more atmospheric drag causing the fragment velocity to slow down rapidly, resulting in a reduced kinetic energy on the target. It can be appreciated that inconsistant fragment size, shape and weight are undesirable.

Heretofore, fragmentation control has included providing grooves on either the external or internal surfaces of the wall of the case or a liner inserted into the case. The grooves create stress concentrations that cause the case to fracture along the grooves forming fragments. Generally these grooves are longitudinal, circumferential, or both, or constitute a series of intersecting helical grooves designed to produce diamond shape fragments. While these devices have demonstrated the ability to create fragments, they are not completely satisfactory for several reasons.

First, the fragments are often much smaller than they ordinarily should be due to fragment weight loss during the fragmentation process. Allowance for weight loss requires that the device be designed to produce larger fragments than will actually result. This reduces the number of fragments available for a given warhead. Second, the prior art devices produce fragments of a variety of weights and do eliminate the variations in kinetic energy resulting therefrom. Additionally, diamond shaped fragments have high drag coefficients, which as stated, result in rapid decay of fragment velocity.

Casings that are relatively thick are susceptible to producing fragments of varying shapes and weights. The helical grooves heretofore utilized are ineffective in controlling these fragment variations. Finally, during the fragmentation process much energy is wasted on metal deformation. Frequently, the corners of the fragments are turned up which further increases drag. It is desirable to provide the device with means for increasing the amount of energy directed to fragmentation rather than being wasted in fragment deformation.

Fragmentation structures, such as fragmentation warheads, mines, etc., are employed by the military against a wide variety of targets where dispersion of fragments over a target area is required. A problem which arises in their use is that fragmentation warheads suitable for use against personnel are generally not suitable for use against "hard" targets such as armored vehicles and emplacements, where fragments of relatively greater size and mass are required. Military units have therefore been required to maintain supplies of several types of fragmentation warheads, each type adapted for use against a particular type of target. This results in an increased burden of logistics and supply and is, of course, highly undesirable.

It has been attempted to minimize this problem by constructing warheads having two sections, one section being adapted to disperse fragments of one size and the other being adapted to disperse fragments of another size. In this manner, a single warhead may be utilized against a variety of targets. Such a construction, however, is inefficient in that, in each case, portions of the warhead not designed for the particular application are largely ineffective; furthermore, in order to produce a given amount of destructive force, a warhead of larger dimensions is necessary than would be the case for one designed for the specific application.

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Other problems related to the construction of fragmentation warheads have involved the expense of machining or casting a multiplicity of grooves or openings in the metal casings to induce fragmentation of the casing in a desired pattern by establishing preferential fracture lines. Alternatively, an inner casing having openings or grooves formed therethrough is disposed within an outer metal casing and configured such that it directs explosive shock waves from an internal explosive charge against the outer casing in a grid-like pattern, such that the outer casing is fractured along the grid lines. In all cases, the molding, machining, or forging of metal structures into a desired, grid-like pattern is undesirably expensive, particularly when large quantities of weapons are to be manufactured.

A further, related problem present with any explosive device is the danger of accidental detonation of the explosive charge by either mechanical shock or heat. Under combat conditions, for example, stored ammunition may be jarred by incoming rounds or careless handling, or it may be heated by fires started by incoming rounds. In any case, it is desirable that the ammunition be as resistant as possible to such heat and shock.

One prior approach to inducing fragmentation control to an integral warhead and missile structure has been to include grooves on either the external or internal wall surfaces of the structure to delineate fragments or projectiles in a combined warhead and missile structure. Explosives are installed in proximity to the grooves. When the explosives are detonated, the grooves create stress concentrations that cause the structure to fracture along the grooves, forming fragments. Generally, these grooves are longitudinal, circumferential, or both, designed to form rectangular fragments, or constitute a series of intersecting helical grooves designed to produced diamond shaped fragments.

Still another approach is the dual-wall naturally fragmenting (and combination natural fragmenting and scored wall) warhead. While these types of warheads have provided somewhat of an improvement over single-wall naturally fragmenting warheads, current dual-wall designs generally require thermal conditioning (i.e., both hot and cold temperature treatment) manufacturing methods to mate walls together with tight circumferential tolerances. However, the thermal conditioning processing steps are time consuming and expensive to implement.

Shrapnel

Common usage distinguishes between a gunshot wound and a shrapnel wound. More precise usage would term the later a fragment wound. Strictly defined, shrapnel means preformed fragments (the fragments exist already made within the explosive munition). Thus, fragmenrs from a random-fragmentation shell are not shrapnel. Also note that by strict definition, flechettes are shrapnel.

In application it has been shown historically that ammunition designed for the distribution of preformed fragments have been more effective against personnel and materials than explosive munitions dependant upon shell casing fragmentation for effectiveness. Typically this type of artillery munition consisted of thin walled frangible

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shells which were randomly filled with spherical shot and fired directly at a target, and were the predominate type used for hundreds of years.

In naval, coast defense and artillery operations, several types of explosive shells are used; the chief ones are: the armor-piercing shell, made to pierce armor plate before exploding; shells exploded by means of a timing fuse; shells exploded by either a timing or percussion fuse; and shells exploded by percussion only. Each different shell has some definite function to fulfill, and is designed for that purpose. For field or artillery operations, the shrapnel and lyddite are the two principal types used. Of these, shrapnel is the most prominent, because of its destructive power and its interesting mechanical construction.

The bursting charge may be located either in the front or in the rear of the shell, whose walls are thinner than in the case of ordinary shell. The bursting charge may also be contained in a central tube, as is the case of navy shrapnel, which may be larger than that used in field pieces. Shrapnel is designed for use against troops in open country or for clearing covered spaces, destructive effect over a considerable area rather than penetrative power being desired. With this in view the fuze is so adjusted that the projectile bursts in close vicinity to the target and scatters its fragments and the balls, which may be placed either in metal or wooden frames or plates or in a matrix of resin. In naval warfare shrapnel is used against attack by torpedo boats or small boats.

The shrapnel shell was invented in 1784 by Lieut. Henry Shrapnel, and was adopted by the British Government in 1808. This first shell was spherical in shape, and the powder or explosive charge was mixed with the bullets. Although this type of shell was an improvement over the grape and canister previously used, its action was not altogether satisfactory, as the shell, on bursting, projected the bullets in all directions and there was also a liability of premature explosion.

In order to overcome the defects mentioned, Col. Boxer separated the bullets from the bursting charge by a sheet-iron diaphragm. This shell was called a diaphragm shell to differentiate it from the first shell of this type. In the shell made by Col. Boxer, the lead bullets were hardened by the addition of antimony, and as the bursting charge was small, the shell was weakened by cutting four grooves extending from the fuse hole to the opposite side of the shell.

Shells of spherical shape were first fired out of plain-bored guns, and upon the advent of the rifled gun it was necessary to add a circular base, which was made of wood and covered with sheet iron or steel to take the rifling grooves. The first shrapnel shells were made of cast iron, but a later development was to use steel and elongate the body, reducing it in diameter. The diameter of the bullets was also reduced so that a greater number could be contained in a slightly smaller space. The improved shrapnel was also capable of being more accurately directed.

By the end of the nineteenth century shrapnel shells, as used by the different governments, varied slightly in construction and general contour as well as in the

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constituents entering into their different members. A completed shrapnel comprises a brass case carrying a detonating primer and the explosive charge for propelling the projectile out of the bore of the gun. The projectile itself comprises a forged shell that carries the lead bullets and bursting charge. Screwed into the front end is the combination timing and percussion fuse which can be set so as to explode the shell at any desired point, and from which the flame for exploding the bursting charge is conveyed through a powder timing train and a tube filled with powder pellets down through the diaphragm to the powder pocket.

A further improvement in the art was seen in U.S. Pat. No. 2,767,656 R. J. Zeamer in which the spherical shot was replaced with cylindrical slugs in closely arranged and stacked in self supporting vertical columns within a semi-frangible shell casing having a predefined release control. This was an improvement over similar munitions using spherical shot for target saturation with preformed fragments, but it lacked effectiveness in long-range applications.

An further improvement in the art was seen in the U.S. Pat. No. 3,956,990 John F. Rose in which the munition consisted of preformed fragments consisting of small finned darts, known in the art as flechettes, being assembled in round clusters and stacked within a semi-frangible shell body in layers separated by metallic disks and support rings. A base exploding charge activated by a fuse when the shell was in the proximity to the target dispenses the flechette clusters and support assemblies. This type of flechette packing has been the conventional standard for artillery and rocket munition use since it's invention.

Conventional fragmentation type of warheads, bombs, rockets and the like have an annular body with an explosive charge in the center and rows of fragments or rods assembled around the center and contained in a thin outer cylindrical casing, for example. Some designs employ a solid type structure surrounding the explosive core, which splits into fragments at specially weakened points when the charge is set off. To penetrate an armored target when the fragments are thrown out by the high explosive, such fragments are designed to have as high a ballistic coefficient as possible, achieved by high density material and low cross-section area in the direction of travel, and to have high explosive launch velocity.

Anti-personnel fragmentation munitions are designed to destroy or maim personnel or to damage material enough to render it inoperable. In the area of field artillery, the flechette or beehive round is an example of an anti-personnel warhead. The payload in this projectile consists of 8,000 steel-wire, fin-stabilized darts. Upon detonation the darts, or flechettes, are sprayed radially from the point of detonation, normally within sixty feet of the ground. It is extremely effective against personnel in the open or in dense foliage.

Armor-Piercing Projectile Armor-Piercing Projectile, known and abbreviated as an A.P. projectile, is one, as may be implied from the name, designed to pierce heavy armor plate, such as found protecting the vital parts of dreadnoughts. The depth to which this projectile will penetrate armor is greater than that of any other manufactured, but depends, of course, on the caliber of the projectile and velocity with which fired from the

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gun. A projectile fired from a high-power 14-inch gun will penetrate armor plate over 16 inches thick at a distance of 9000 yards. Armor serves two purposes: first, protection for the personnel, which involves that of the gun-positions and armament ; and, second, protection for the floatability and interior mechanism of the vessel. The latter includes protection of the hull and machinery. This protection is afforded to as great an extent as possible on early 20th Century warships by the armor-belt, extending the whole length of the ship, the side-armor and casemate-armor, the protective deck, turrets, barbettes, gun-shields, and armored conning-tovvers. For use against war vessels, by the end of the 19th Century forged steel projectiles were divided into shot and shell; the former ws a misnomer as the shot is really a shell, in that it contained a bursting charge. The only difference between the shot and shell is that the latter has a cavity accommodating a bursting charge approximately three times as large as that in the former. When these projectiles were first made, no explosive then known was sufficient in power to burst the shot, and the cavity was made merely for the purpose of obtaining a better forging. With the invention of Maximite, and later of Dunnite, for bursting charges, it was found that the shot could be exploded, and all armor piercing projectiles are now loaded with the bursting charge, and fuzed. At the end of the 19th Century only at shorter ranges can the belt armor of the heavier warships be pierced. At the longer ranges only the lighter armor can be pierced, but a sufficient number of hits, combined with the racking effect of the great bursting charge, would serve to put a warship out of action. For these longer ranges, then, the shell is used with its thinner walls, greater explosive charge, and an instantaneous fuse. At the near ranges, where actual perforation of the belt armor can be obtained, the armor piercing shot is used, with its heavy walls strong enough to stand the shock of impact, and supplied with a delayed action fuse which holds up the explosion of the bursting charge until the projectile has had time to penetrate to the vitals of the vessel. The earliest armor, both for ships and forts, was made of wrought iron, and was disposed either in a single thickness or successive layers sandwiched with wood or concrete. The first armor-piercing shell were designed by Sir W. Palliser, of England, and were made of chilled iron, or steel, with ogival shaped heads, a form combining strength and sharpness. They were filled with powder introduced through a hole in the base, which was subsequently closed by a strong screw- plug. They were fitted with percussion fuses, arranged to explode them the instant after impact. A 4.5-in. steel shield for the US government, face-hardened by the Harvey process, was attacked by 5-inch and 6-inch armour-piercing shot, and proved capable of keeping out the 5-in. up to a striking velocity of nearly 1,800 ft, per second, but was defeated by a 6-in. capped A.P. shot with a striking velocity of 1,842 ft. per second. Chilled iron, on account of its liability to break up when subjected to a continuous bombardment by the armor-piercing steel projectiles of guns of even medium calibre, was usually considered unsuitable for employment in inland forts, where wrought iron, mild steel or compound armor was preferred. On the other hand, it was admirably adapted to resist the few rounds that the heavy guns of battleships might be expected to deliver during an attack of comparatively limited duration. Chilled iron was never employed for naval purposes, and warship armor continued to be made exclusively of wrought iron until 1876 when steel was introduced by Schneider. As steel improved, efforts were made to impart an even greater hardness to the actual surface or skin of compound armour, and, with this object in view, Captain T. J. Tresidder, C.M.G., patented in 1887 a method of chilling the heated surface of a plate

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by means of jets of water under pressure. The inherent defect of compound armor, its want of homogeneity, remained, and in the year 1891 H. A. Harvey of Newark, N.J., introduced a process whereby an all steel plate could be face-hardened in such a way that the advantages of the compound principle were obtained in a homogeneous plate. The process in question consisted in carburizing or cementing the surface of a steel plate by keeping it for a fortnight or so at a high temperature in contact with finely divided charcoal, so that the heated surface absorbed a certain amount of carbon, which penetrated to a considerable depth, thus causing a difference in chemical composition between the front and back of the plate. Steel plates treated by the Harvey and Tresidder processes, which shortly became combined, possessed about twice the resisting power of wrought iron. The figure of merit, or resistance to penetration as compared with wrought iron, varied with the thickness of the plate, being rather more than 2 with plates from 6 to 8 in. thick and rather less for the thicker plates. In 1889 Schneider introduced the use of nickel in steel for armor plates, and in 1891 or 1892 the St Chamcmd works employed a nickel steel to which was added a small percentage of chromium. Krupp plates are made of nickel-chrome steel and undergo a special heat treatment during manufacture. The resisting power of the non-cemented Krupp plates is usually regarded as being considerably less than that of the cemented plates, and may be taken on an average to be 2-25 times that of wrought iron. At the time of the Great War manufacture of armor-piercing projectiles began with ingots of the necessary size and containing the required extra metal formed in projectile molds. The charge is made up of from 50 per cent to 75 per cent of pig iron or wrought iron (pig iron in open-hearth process, wrought iron in crucible process), metallic nickel, ferro-chromium, ferro-manganese, ferro-silicon, and projectile scrap, i.e., discard taken from the base ends of projectiles. Carbon may also be added, if necessary. After casting, ingots are reheated and forged to a desired form under a hammer, forging-dies being used. The blanks are then annealed to take out stresses, after which they are sent to the machine shop. From the machine shop the shells go to the treating-house, where they are specially hardened and where their bases are annealed. After final treatment the shells are subject to the immersion test in hot and cold water. Chemical and physical tests are made for the purpose of insuring- uniformity in each lot, and while not specifying the amount of carbon, nickel, or chromium, or other hardening element, a specimen from each heat is analyzed and the percentage determined, which is not permitted to vary more than a certain specified amount from the mean percentage of carbon, chromium, and nickel of the entire lot. By the time of the Great War practically all Naval projectiles above 7 inches in caliber were either armor-piercing or high-capacity, the armor-piercing having thick walls and being loaded with explosive "D," detonated by a delayed-action high-explosive exterior fuse called the Semple tracer detonator. The weight of the explosive, which is sufficient to fragment the shell, is from 2 to 3 per cent of the gross weight. A typical armor-piercing projectile had the same general dimensions and the ogival head and point described for projectiles in general. This point is extremely hard and well tempered. Over the ogival head and point is a cap. This is made of comparatively, soft steel and is rigidly secured to the projectile proper by an undercut score in the head. The end of the Cap is very blunt, little metal being in front of the point of the projectile. The theory or reason of the soft steel cap on armor-piercing projectiles is, that when fired, the entire weight of the projectile is utilized; first, to bend in the armor plate to a degree near its breaking point. In this process the soft steel cap is

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crushed down around the sides of the ogival head of the projectile. Now, inasmuch as the point of the projectile is very hard and sharp, the whole projectile continues its motion forward, the hard sharp point cutting right through the soft steel cap, striking, in a sense, another blow on the armor plate. The point of the projectile now pierces the already scaled plate and the projectile itself enters through and explodes in the rear of the armor plate, or on the inside of the vessel. The only difficulty in the satisfactory use of this soft steel cap now presents itself. The very blunt end or large flat area at the head of the projectile offers too much resistance to the air in its flight and therefore materially reduces the effective range. To overcome this difficulty there is screwed on to the blunt, forward end of the Cap another small, soft steel cap, this last cap being hollow. This cap is sometimes designated as a wind-shield for the reason that it brings the projectile practically to a point, and reduces to a negligible quantity the air resistance encountered by the blunt end of the Cap. It is also known as a thimble from its shape and its hollowness. It is made hollow in order that no metal be massed in front of the point of the projectile, which is objectionable, as has been explained before. At low striking velocities, probably in the neighbourhood of 1700 ft. per second, the cap fails to act, and no advantage is given by it 10 the shot. This is probably because the velocity is sufficiently low to give the cap time to expand and so fail to grip the point as the latter is forced into it. The cap also fails as a rule to benefit the projectile when the angle of incidence is more than 30 degrees to the normal. Projectiles striking armor at an angle of more than 10° from normal are subjected to severe cross-breaking stresses, and it is not expected that penetration will be effected under such conditions unless the projectile considerably overmatches the armor. Summing up on the use of the combined soft steel cap, the long, tapering cap gives a range equal to or greater than that attained by the ogival-headed projectile; gives a better trajectory to the projectile; and gives a considerably higher striking velocity at equal ranges than an uncapped projectile. By the time of the Great War it had been established beyond doubt, by exhaustive experiments, that under certain conditions capped shell may even pierce armor that has the balance of power, armor for which uncapped shells are no match under the same conditions. Although forms for caps which increase the efficiency of armor-piercing projectiles had been worked out in all nations in an empirical manner, there was no unity regarding theories as to the manner in which the caps attain their results. Deck piercing projectiles for coastal defense mortars wre similar to the armor piercing shell in that they had thin walls, and a large bursting charge, but are provided with a delayed action fuze, in order that the projectile may have penetrated the decks of a warship, including the protective deck, which covers the engine rooms and magazine, before the fuze operates to explode the bursting charge. Around 1900 the problem of penetrating the sides of armored vessels being so difficult, attempts were made to perforate their decks. When the weight of guns, machinery, and armor carried by ships of the day was considered, the available vyeight left for deck protection was comparatively small, and hence a thickness of about 4-1/2 inches of protective deck was about all that can be carried. Against these decks. the vertical fire of shell from heavy rifled mortars was directed. Since the thickness of plate to be penetrated was not great, the walls of the shell for these mortars need not be very thick, hence they have great interior capacity, carry heavy bursting charges, and their effect is very destructive. The disadvantage is, the difficulty of hitting the object ; but this is compensated for by increasing the number of mortars. High Explosive(HE)"; case

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1100: return "HE, Plastic"; case 1200: return "HE, Incendiary"; case 1300: return "HE, Fragmentation"; case 1400: return "HE, Antitank"; case 1500: return "HE, Bomblets"; case 1600: return "HE, Shaped Charge"; case 1610: return "HE, Continuous Rod"; case 1615: return "HE, Tungsten Ball"; case 1620: return "HE, Blast Fragmentation"; case 1625: return "HE, Steerable Darts with HE"; case 1630: return "HE, Darts"; case 1635: return "HE, Flechettes"; case 1640: return "HE, Directed Fragmentation"; case 1645: return "HE, Semi-Armor Piercing (SAP)"; case 1650: return "HE, Shaped Charge Fragmentation"; case 1655: return "HE, Semi-Armor Piercing, Fragmentation"; case 1660: return "HE, Hallow Charge"; case 1665: return "HE, Double Hallow Charge"; case 1670: return "HE, General Purpose"; case 1675: return "HE, Blast Penetrator"; case 1680: return "HE, Rod Penetrator"; case 1685: return "HE, Antipersonnel"; case 2000: return "Smoke"; case 3000: return "Illumination"; case 4000: return "Practice"; case 5000: return "Kinetic"; case 6000: return "Mines"; Survivability is defined as the capacity of the ship to absorb damage and maintain mission integrity. The ability to effect major survivability improvements becomes difficult once the fundamental design trade-off decisions have been made. These decisions usually occur during the early design phases of the ship acquisition process. Since the installation of survivability improvements into existing ships has proven very expensive, a forward fit strategy is necessary to achieve high pay-off results. Focus on incorporating survivability features in the early phases of ship design will ensure an affordable balance of desired upgrades in the Top Level Requirements (TLRS) for each new ship class. Warships are expected to perform offensive missions, sustain battle damage and survive. As such, the total ship, comprised of combat systems and vital hull, mechanical and electrical components, must be sufficiently hardened to withstand designated threat levels. Enhancement techniques, such as equipment separation and redundancy, arrangements and personnel protection form an integral part of this effort. DC/FF training and associated maintenance of ship survivability features are also essential elements to ensure sustained capability. Survivability is considered a fundamental design requirement of no less significance than other inherent ship characteristics, such as weight and stability margins, maneuverability, structural integrity and combat systems capability. The Chief of Naval Operation’s (CNO’S) goal is to maintain ship operational readiness and preserve warfighting capability in both peacetime and hostile environments. Ship protection features, such as armor, shielding and signature reduction, together with installed equipment hardened to appropriate standards, constitute a minimum baseline of survivability. These shall be implemented through appropriate ship and equipment specifications and the application of the principles of separation, redundancy and arrangements of critical components and systems. Major overhaul and modernization programs shall incorporate survivability enhancement features wherever practical and affordable. Survivability weapons effects and operational environments are categorized in terms of the three levels of severity described below. They provide a basis for establishing survivability performance standards and are not intended to describe conditions of readiness or misfin impact. Ship survivability features shall provide affordable protection to support sustained mission capability: Level I - low represents the least severe environment anticipated and excludes the need for enhanced survivability for designated ship classes to sustain operations in the immediate area of an engaged Battle Group or in the general war-at-sea region. In this category, the minimum design capability required shall, in addition to the inherent sea

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keeping mission, provide for EMP and shock hardening, individual protection for CBR, including decontamination stations, the DC/FF capability to control and recover from conflagrations and include the ability to operate in a high latitude environment. Level II - moderate represents an increase of severity to include the ability for sustained operations when in support of a Battle Group and in the general war-at-sea area. This level shall provide the ability for sustained combat operations following weapons impact. Capabilities shall include the requirements of Level I plus primary and support system redundancy, collective protection system, improved structural integrity and subdivision, fragmentation protection, signature reduction, conventional and nuclear blast protection and nuclear hardening. Level III - high, the most severe environment projected for combatant Battle Groups, shall include the requirements of Level II plus the ability to deal with the broad degrading effects of damage from anti-ship cruise missiles (ASCMS), torpedoes and mines. Semi-Armor Piercing (SAP) Common Shell Semi-Armor Piercing Warheads are designed to penetrate into the target and detonate, posing a blast/fragmentation threat to structures and vital systems. One predominant class of threat weapon in the early 21st Century is the anti-ship cruise missile carrying a semi-armor piercing warhead designed to penetrate the hull and detonate inside. It creates a shock wave and a large amount of high-pressure gas. When contained, this can rupture bulkheads and doors, expanding the damage area, allowing fire and flooding throughout the ship. The loading may rupture bulkheads by causing the connection to the deck to fail, forcing it out of the way. The use of commercial construction practices may affect the pressure at which the bulkheads fail because the connection details are different. A common shell is a hollow cylindrical casting having an ogival head. The term came into use in the early 19th Century, and remained in use through the early 20th Century. Common shell have been made of cast-iron, cast-steel, and forged-steel. The forged-steel shell, being tough and having good penetrating power, has sometimes been called "the semi-armor-piercing shell." The term common shell was preferred by the early 20th Century US Navy, however. The US Navy differerntiated between the common shell and high explosive shell, the later having a higher proportion of explosive fill and a corresponding thinner case. By 1898 five kinds of projectiles were used in the US Navy — armor-piercing, semi-armor-piercing, common cast-iron, shrapnel, and canister. With the exception of canister, all other shells contain bursting charges, but naturally the bursting eñ'ect of the semi armor-piercing shells is much greater than that of the armor piercing. In an attack upon earthworks the semi-armor-picrcing shells would be used ; while against unarmored ships common shell and shrapnel would be employed. In an attack upon an ironclad possessing no unannored superstructures (monitors), armor-piercing shells would be used exclusively; but when opposing battleships, which present large unarmored surfaces, both kinds of shells may be employed. Some guns whould be loaded with armor-piercing and others with semi-armor-piercing shells. When semi-armor-piercing shells strike armor, they do not pierce it, but when they strike unarmored parts they do more injury than the armor piercing. If an antagonist possesses no thin armor, but only heavy plates, medium-caliber guns, which are unable to pierce thick armor, would be loaded exclusively with semi-armor- piercing shells. In the early 20th Century three kinds of projectiles were in use in the U.S. Navy for the large caliber guns : Armor-piercing, common or semi-armor piercing, and shrapnel. As a rule the latter would only be used in the attack of exposed bodies of men. The specifications for the former

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require that armor-piercing shell shall perforate face-hardened armor-plate of thickness equal to the caliber, and remain in a condition for effective bursting. Semi-armor piercing, or forged-steel shell, must pass through half a caliber of face-hardened armor and remain in a condition for effective bursting. Armor-piercing projectiles of the early 20th century were made solid, or practically so, a small core being formed to give the best results in the forging process. The semi-armor-piercing was formed hollow, with a core of moderate dimensions, large enough to hold an explosive charge that will insure the bursting of the thick walls of the projectile. It is made of chrome steel, and requires in its manufacture to be treated with great care to secure the combined hardness and toughness to enable it to pierce solid armor without fracturing and carry its explosive charge intact into the interior of the ship. When such shell is filled with common powder the heat engendered by passing through the armor is depended on to explode the shell just within the ship; no fuse was used. A common shell is filled with powder which forms the bursting charge, and is fitted with either a time or percussion fuze, according to the nature of ordnance from which it is fired. The use of this shell is for all purposes where great destructive effect is required, such as against men in masses, buildings, shipping, and material generally, either by bursting during flight or at rest, when the shell acts as a mine. It is used particularly in the field when the enemy is sheltered from direct fire, or against cavalry to frighten the horses and create confusion. In the early 20th Century warship provided one thickness of armor for protection against armor-piercing projectiles and another for defense against common shell. At the battle of Tsushima there was not only no penetration of the heavy armor, but even the light armor was pierced on extraordinarily few occasions taking into account the enormous number of hits (the case of the Orel, for example). The same thing was observed in the Chino-Japanese war, at the battle of the Yalu, and in the Spanish-American war at Santiago. For the moment, the penetration of armor seemed unattainable with present equipment. Russian war experience in 1904 showed that a common shell, even if it strikes on the most heavily armored part, sets up such a concussion that the protecting armor is shattered and cracks appear in the side of the ship, through which water is irresistibly forced. A very good example of this was the Retvizan which on February 26, 1904, was hit by five common shell, one of them striking on the most heavily armored part near the waterline, at a range of nine miles; the armor was not pierced, but the concussion was such that a leak appeared which was overcome only with the greatest difficulty. Hits from armor piercing and common shell may be easily distinguished also in the lightly protected parts by the difference in the damage inflicted. The common shell causes damage over a surface of 100 square feet, driving into the ship rivets and portions of the hull. Besides this it discharges an immense amount of gas heated to an enormous temperature which consumes everything, and envelopes the ship for quite a long time in a dense suffocating atmosphere. The armor piercing shell with its small bursting charge produces a comparatively slight effect, for even if it does penetrate, it makes an exceedingly small hole and as its burst takes place after penetration, the only effect is a shower of splinters. From these considerations, it would appear that the only possible projectile against a ship is the common shell with instantaneous fuze, as its effect extends over the whole surface of the ship, and does not depend either on the angle of impact or on the range. This then is one consideration which will influence the choice of weapon for coast armaments. Before the Great War the study of projectiles in France and Germany developed from

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different definitions of effectiveness. A fragment was effective, according to French definitions, when it passed through a pine panel 41 mm. thick. In Germany the standard thickness was much less (about one-half). It will easily be understood that different types of shell developed in the two countries. The German shell does not pass through a plate of special steel 20 mm. thick. To fight tanks the Germans therefore developed a special projectile. This projectile is derived from the model 1915 explosive shell which was transformed into a semi-armor-piercing shell. A massive ogive of hard steel is screwed on the shell body, which has been duly adapted to receive it. The front of the ogive terminates in a flat nose 20 mm. in diameter. At the bottom of the cavity is a metal box containing a smoke-generating substance. This box is separated from the explosive by a layer of pitch. In the early 20th Century the US Army classified shells as common shell and high explosive shell. The US Army's common shell [which was more or less obsolete at that time] was a hollow cast-iron cylinder with an ogival head and contains a bursting charge of black powder. The high explosive shell is of practically the same shape and dimensions as the common shell, but was made of steel and contains a bursting charge of high explosive (a picric acid compound). The bursting charge in both the common and high explosive shell is exploded by percussion fuse. Either shell may be characterized as a flying mine, the chief object of which is to destroy material objects at a distance, although either may be used effectively against troops. The standard design for metal-piercing ammunition includes a hardened steel penetrator encased by a soft metal jacket to prevent damage rifling in the base of the weapon as the ammunition is discharged. The jacket is usually composed of a soft metal called gilding metal while the nose or piercing end is steel or some other hard metal. The jacket also operates as a windshield by reducing aerodynamic drag thereby control the amount of energy lost between the nozzle of the gun and the target. In the 21st Century, General-purpose (GP) bombs are used against unarmored ships or ground targets for blast or fragmentation. Fragmentation bombs are very small explosives dropped in clusters against troops and ground targets. Semi-armor-piercing (SAP) bombs are used against carriers, cruisers, and "hardened" ground targets. High-Capacity Shells High-capacity shells have the same external appearance as an armor-piercing projectile without a soft steel cap. These shells are made for large-caliber guns only, and are designed, not to pierce heavy armor plate, but to destroy the upper works of battleships and pierce comparatively thin armor. With this end in view the walls of the shell are made thinner than those of armor-piercing projectiles and the seat of the bursting charge very much larger. In the United States at the beginning of the 20th Century the bursting charge consisted of "Explosive D" and weighs up to 10% of the entire weight of the projectile, as compared with a relative weight of from 2% to 3% of bursting charge in an armor-piercing projectile. High-capacity shells are otherwise fitted with base plugs, fuses, tracers, etc., of the same types as armor-piercing projectiles of corresponding calibers. Prior to the Great War, it had been apparent to the US Navy that naval guns might be called upon to participate in land operations, either by actual bombardment by the fleet or by use of naval guns ashore, and the design of suitable projectiles was developed. Immediately that funds were available therefor, the Bureau of Ordnance, in March 1917, contracted for a supply of approximately 3,000 special high capacity, high-explosive projectiles, for the Navy's standard 14-inch guns; and the delivery of this entire order was completed in December, 1917. The wisdom of this move was later demonstrated, when the Navy railway battery was proposed, and these

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projectiles were used in France by that battery. It is interesting, in this connection, to note that the Navy turned over to the Army approximately 50 per cent of these projectiles, which number was in excess of the Navy's needs for its own batteries, for use in similar guns. Similarly, it was decided that a high capacity, high-explosive projectile would be exceedingly effective for the high power 7-inch naval guns which were being made available for use ashore, and, on April 25, 1918, the bureau placed orders for a considerable quantity of such projectiles. Within one month of the placing of this contract, deliveries of projectiles had commenced. These projectiles were assigned to the 7-inch tractor mounts, when that project was launched. This type of projectile was exceedingly useful for such purposes and gave excellent range qualities. BLIND OR TARGET projectiles are made of cast steel or cast iron. They have the external appearance of a capped armor-piercing projectile. The only use of these projectiles is in target practice. The cavity is filled usually with sand, but can be filled with any substance which will give the shell the desired weight. These projectiles are never fitted with fuses and have no bursting charge, but do have tracers when used in night practice. They are essentially "blind" or "dummy" shells; their only requisites being shape and weight. When the bomb Is released from the plane a pin on the release mechanism is caught in the loop of the safety wire, thus withdrawing the other end from the hole in the safety pin. The action of the spring throws off the safety pin, which releases the detonator. As soon as the bomb has assumed a vertical position the detonator slides forward. Its forward movement, however, is retarded by the cushion of air underneath it, there being but little clearance between the detonator and the booster cup tube. In this manner the detonator Is seated gently on the lead safety pin. When the bomb comes in contact with any object the detonator Is driven forward by inertia, the lead pin is bent or crushed, and the primer strikes the firing pin. The flash from the primer Ignites the black-powder train, this explodes the fulminate, which is now inside the booster cup. The booster charge is thus detonated, in turn detonating the main charge. The high-capacity drop bomb, Mark II, is provided with a special front cap and auxiliary safety wire, in order that it may also be used in connection with the vertical release mechanism. The shell cap Is similar in shape to those on the Mark I and Mark III. It is a steel cone, 15/16 of an inch high and 2.13 inches at its largest diameter. A cylinder 3/16 of an inch long projects from the base of the cone, and is threaded to a diameter of 1-3/8 inches to fit into the front bushing. At a point 1/2 inch from the front end a recess is cut around the conical portion/ 1/4 of an inch wide and 1 inch in diameter, to receive the jaws of the release mechanism. A hole 3/16 of an inch in diameter and 1/4 of an inch deep is drilled into this surface to provide a grip for a wrench.

Shaped Charge

The discovery of what is variously referred to as the shaped charge effect, the hollow charge effect, the cavity effect, or the Munroe Effect, dates back to the 1888 in the US. Dr. Charles Munroe, while working at the Naval Torpedo Station at Newport, Rhode Island, in the 1880s, discovered that if a block of guncotton with letters countersunk into its surface was detonated with its lettered surface against a steel plate, the letters were indented into the surface of the steel. The essential features of this effect were also

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observed in about 1880 in both Germany and Norway, although no great use was made of it, and it was temporarily forgotten.

Charles Munroe (1849-1938), the inventor of smokeless gunpowder, was head of the Department of Chemistry and the Dean of the Corcoran Scientific School at Columbian University (which became George Washington University in 1904.) between 1892 and 1898. Munroe was considered one of the world's authorities on explosives, and authored more than 100 books on that subject, as well as chemistry. He was the recipient of numerous honors from governments and scientific societies, including an appointment in 1900 by the Swedish Academy of Science to nominate the candidate for the Nobel Prize in chemistry. Munroe served as president of the American Chemical Society and fellow of the Chemical Society of London. Domestically, he was a consultant to the US Geological Survey and the US Bureau of Mines.

Von Foerster was the true discoverer of the modern hollow charge [Hohlladung]. A pair of Swiss inventors were the first to think of using the well documented Munroe Effect to penetrate armor plate. They tried to sell the design to foreign arms manufacturers, claiming that a new explosive had been discovered. Unfortunately for the inventors, explosives experts soon figured out that a shaped charge was responsible for the amazing penetration results, and they went ahead and copied it. The United States was the first to use these shaped charge in the late 1930's as an anti-tank weapon; the Soviet Union, Germany, and Great Britain followed as early as 1940. The worlds first anti-tank weapon using the hollow charge was the German "Panzerfaust" [Armoured fist].

A shaped charge warhead consists basically of a hollow liner of metal material, usually copper or aluminum of conical, hemispherical, or other shape, backed on the convex side by explosive. A container, fuze, and detonating device are included.

When this warhead strikes a target, the fuze detonates the charge from the rear. A detonation wave sweeps forward and begins to collapse the metal cone liner at its apex. The collapse of the cone results in the formation and ejection of a continuous high-velocity molten jet of liner material. Velocity of the tip of the jet is on order of 8,500 meters per sec, while the trail-ing end of the jet has a velocity on the order of 1,500 meters per sec. This produces a velocity gradient that tends to stretch out or lengthen the jet. The jet is then followed by a slug that consists of about 80% of the liner mass. The slug has a velocity on the order of 600 meters per sec.

The penetration depth of the jet depends on the length of the jet upon impact, and its relative density towards that of the target material. Since the jet stretches during its flight, a better performance is obtained using a standoff between the perforating charge and the target. At larger standoff, the jet is broken into many small particulates that show much less penetrating power than a continuous jet.

When the jet strikes a target of armor plate or mild steel, pressures in the range of hundreds of kilobars are produced at the point of contact. This pressure produces stresses far above the yield strength of steel, and the target material flows like a fluid out of the

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path of the jet. This phenomenon is called hydrodynamic penetration. There is so much radial momentum associated with the flow that the difference in diameter between the jet and the hole it produces depends on the characteristics of the target material. A larger diameter hole will be made in mild steel than in armor plate because the density and hardness of armor plate is greater. The depth of penetration into a very thick slab of mild steel will also be greater than that into homogeneous armor.

In general, the depth of penetration depends upon five factors:

Length of jet Density of the target material Hardness of target material Density of the jet Jet precision (straight vs. divergent)

The longer the jet, the greater the depth of penetration. Therefore, the greater the standoff distance (distance from target to base of cone) the better. This is true up to the point at which the jet particulates or breaks up (at 6 to 8 cone diameters from the cone base). Particulation is a result of the velocity gradient in the jet, which stretches it out until it breaks up.

Jet precision refers to the straightness of the jet. If the jet is formed with some oscillation or wavy motion, then depth of penetration will be reduced. This is a function of the quality of the liner and the initial detonation location accuracy. The effectiveness of shaped charge warheads is reduced when they are caused to rotate. Spin-stabilized projectiles generally cannot use shaped-charge warheads.

Pyrotechnics

Pyrotechnics are typically employed for signaling, illuminating, or marking targets.

Illumination--These warheads usually contain a flare or magnesium flare candle as the payload, which is expelled by a small charge and is parachuted to the ground. During its descent the flare is kindled. The illuminating warhead is thus of great usefulness during night attacks in pointing out enemy fortifications. Because these flares are difficult to extinguish if accidentally ignited, extreme caution in their handling is required.

Smoke--These munitions are used primarily to screen troop movements and play a vital role in battlefield tactics. A black powder charge ignites and expels canisters that may be designed to emit white, yellow, red, green, or violet smoke.

Markers--White phosphorus is commonly employed as a pay-load to mark the position of the enemy. It can be very dangerous, especially in heavy concentrations. The material can self-ignite in air, cannot be extinguished by water, and will rekindle upon subsequent exposure to air. Body contact can produce serious burns. Copper sulphate prevents its re-ignition.

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Cluster

Cluster munitions are canisters containing dozens or hundreds of small bomblets for use against a variety of targets, such as personnel, armored ve-hicles, or ships. Once in the air, the canisters open, spreading the bomblets out in a wide pattern. The advantage of this type of warhead is that it gives a wide area of coverage, which allows for a greater margin of error in delivery.

Canister

The APERS [anti-personnel] canister is a gun launched ammunition (round). It may be fired from, for example, a tank or artillery piece. The canister is designed for defeating groups of personnel at various ranges, as opposed to defeating tanks, armored personnel carriers, aircraft, or other vehicle targets. The goal of this type of ammunition, much like a shotgun, is to disperse the payload upon exiting the gun tube and achieve maximum dispersion thus eliminating the maximum number of enemy personnel. As with a shrapnel round, the payload may comprise round tungsten balls, steel rectangular prisms, or flechettes. The cannister round differs from a shrapnel round in that the later is a long range munition that has a bursting charge that detonates in proximity to the target, while the former is a short range spontaneously disperses the chargo at the moment of exiting the gun tube.

Effective close-in support of men and material is a mandatory requirement for modern gun systems. Recent advances in medium caliber, i.e., 20 to 30mm ammunition designs have brought about significant improvements towards this end. For instance, controlled fragmentation high explosive rounds, and multiple flechette rounds have greatly increased the survivability of the modern armed vehicle against ambush. However, these munitions have their limitations.

It was discovered early, in the use of cannon and artillery pieces, that they were no defense against close-up charge of troops. Thus the expedients of the so-called "grape-shot" and the like were developed, wherein a large number of fragments of various forms or shapes were loaded in the weapon and fired at point blank range. This principle was extended further with the development of modern cannister ammunition wherein a shell body was designed specifically for containing a multiplicity of fragments and adapted for firing at point blank range. The ammunition is designed to open substantially immediately after exit from the muzzle of the weapon. The cannister round is the antipersonnel round that essentially bursts at the muzzle.

As is well known in the art, the fragments will disperse in relation to the twist of the rifling in the weapon. Since this ammunition functioned substantially at the muzzle of the

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weapon its beneficial anti-personnel effect could not be utilized at ranges other than essentially point blank. The cannister round is effective from 250 to 500 meters. In the 19th Century, at extremely close ranges of 200 yards or less, artillerymen often loaded double charges of canister.

Prior to the 20th Century field artillery firing was by "direct fire," that is, fire in which the target is in view of the gun. The use of canister artillery rounds was reported as early as the year 1410. Field Artillery guns in the 18th Century were small, with a short range. Solid shot and grape were alone used; explosive shell and shrapnel had not been invented. Canister consisted of a tin cylinder in which was packed a number of iron or lead balls. Upon discharge the cylinder split open and the smaller projectiles fanned out. Canister was an extremely effective antipersonnel weapon, with an effective range of 400 yards. In emergencies double loads of canister could be used at ranges less than 200 yards, using a single propelling charge. One Grape Shot round fired by 19th century Artillery against the advance of Infantry was made up of 36 large metal balls. Once fired, the balls are thrown free, each taking its own path.

The range of smoothbore cannon gradually increased over the years until, by the Napoleonic era, cannon could fire about 300 yards, or about the range of the Roman ballistae. Up until the Crimean War (1854), 70 percent of all cannon shot fired was solid ball shot. But as early as the 1740s artillery gunners had various types of artillery rounds at their disposal. Heavy rounds that exploded on contact were used primarily by howitzers while artillery guns, those with a flatter trajectory, commonly used canister, chain, and grapeshot against cavalry and infantry formations.

An 1856 handbook noted that the canister is broken by the shock of the exploded charge in the piece, and the balls spread themselves out in front of the muzzle in the shape of a cone. They strike the object partly directly, partly by ricochet. As the number of balls which issue from the piece is very considerable, and as, in consequence of their diminutive size, they easily stick or lose their force, when the ground is soft or uneven, it is obvious that the effect of this nature of fire is more dependent upon the nature of the ground than any other. It is only firm even ground which gives good effect, while, on the other hand, meadows, freshly ploughed fields, ditches, ledges of earth, tall tubers, and even fields of corn considerably diminish the effect of this fire. The large balls of the 12-pounder overcome the obstacles of the ground easier than do those of the 6-pounder; the heavier calibre is superior to the lighter by an average of about 200 paces.

Canister shot may be used against the enemy's artillery in the last stages of an attack, in order to put their men and horses hors de combat; it is particularly effective when it can be thrown in on the flank of an enemy's battery. Against field entrenchments, villages, and skirts of woods a lively canister shot fire should precede the storming columns of the infantry. To prevent a thick swarm of tirailleurs from penetrating into the battery it is often the last resort, when musketry fire is incapable of doing so.

Canister shot fire is more equally and surely effective than shrapnell fire ; especially in quick firing and when the object is in motion. It is always to be preferred to shrapnell fire

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in the defence of a battery, when the attacks of the enemy's troops are to be beaten off. Under 600 paces it is annihilating, and decides the fray in a few minutes ; at greater distances, on the other hand, it may in unfavourable ground be ineffective ; it is, therefore, to the interest of the artillery not to deprive themselves of this last decisive measure, by making use of that nature of fire too early ; for an unprofitable canister shot fire causes the enemy to undervalue it.

In the Union Army of 1861 there were four kinds of projectiles used in field service, viz : the SOLID or BOUND SHOT, the OANISTER, the SHELL, and the SPHERICAL CASE SHOT. The projectile is attached to a block of wood called a SABOT. For the guns and the 12-pounder howitzer, the cartridge and the projectile are attached to the same sabot, making together a round of fixed ammunition. For 32-pounder and 24-pounder howitzers, the projectile is separate from the charge, and the cartridge is attached to a block of wood called a cartridge block. The CANISTER consists of a tin cylinder, attached to a sabot and filled with tad-iron shot. These shot vary in diameter, and of course in weight, with the calibre and description of the piece. Canisters for guns contain 27 shots each ; those for howitzers contain 48 shots each. They are packed in sawdust in four tiers ; the lower tier rests on a rolled iron plate, which ;s placed on the sabot, and the canister is closed with a sheet-iron cover. The canister takes its designation from that of the piece for which it is prepared.

An 1878 treatise considered the situation when an armed and turbulent mob exists in a large city, the civil authorities are powerless to suppress violence. As a last resort the military force has been duly and properly called upon. Unless protected by barricades it is not probable that the mob will long withstand the fire from the skirmish line. If the mob is not behind barricades the artillery should use canister (canister being less destructive to property than grape, solid shot, or shell, and probably more effective for this purpose at close range). If the enemy is protected by defenses, it may be necessary to use shell and solid shot to dislodge him.

By around the year 1900 Case-shot, or CANISTER, was an artillery projectile for use at close quarters, and consisted of a sheet-iron or tin cylinder filled with bullets varying from an oz. to 1 Ib. in weight, and in number according* to the size of the gun. The cylinder is closed by discs of wood, tin, or iron, its walls are strengthened by loose pieces of iron, and the interstices between the balls are packed with shavings and sawdust. On discharge the canister breaks up at once, and the bullets spread over a wide area, but with a low velocity. For this reason they have little effect beyond 300 yards, even on haru open ground, which is best suited to their action. Case- shot is chiefly used in the close defence of works, or against cavalry, and at sea against a boat attack. At long ranges its place is taken by Shrapnel Shell.

Over time the grape, canister, and spherical case of field artillery lost ground in the field They were more especially formidable and useful when musketry fire was only available up to 200 yards; but they were superseded when the infantry man with his rifle can in some respects do the work better. The Enfield rifle in the hands of the infantry was

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capable of making a greater proportion of destructive hits between 600 and 1100 yards on a column of men than the artillery with their spherical case.

In the Great War canister had been replaced by shrapnel, which bursts approximately 200 m. in front of the gun when the fuse is set at zero. In canister, the contained bullets have a smaller initial velocity than the case. They richochet on striking. The range of these ricochets depends upon the character of the ground. Solid, level ground, or a gentle downward slope increase their range, whereas snow, sand, wet meadows, ploughed and cultivated land reduce their range. Since the introduction of smokeless powder, the range of canister has decreased, as this powder requires that the projectile close the barrel more tightly than canister is capable of doing. The small dispersion, the superficial direction, and flat trajectory of its individual bullets made canister very effective against standing targets at short ranges. *

In World War II the Bougainville operation began with initial landings taking place on 1 November 1943 and, ended on 28 December 1943. Marines on Bougainville used a "buckshot" antipersonnel round fired from tanks with deadly effect. Medium tanks, closing on known Japanese positions, acted as bait; as the Japanese swarmed over the tank to emplace a charge in order to destroy it, a companion light tank would fire the "buckshot" round directly at the heavier one. The thumbnail-size projectiles would slaughter the attackers but could not penetrate the armor of the vehicle.

The shock effect of even a single tank in guerrilla warfare was apparent in Vietnam. Lieutenant Colonel Ronald J. Fairfield, Commanding Officer, 1st Battalion, 69th Armor, stated, "The NVA/VC have shown a reluctance to engage tanks where they can be avoided."' A year later, Lieutenant Colonel Paul S. Williams, Jr., while commanding the same battalion, said: "Captured documents and interrogation reports disclose that the enemy is afraid of tanks. We feel what he really fears is the cannister round and its effect. This [feeling] has been justified, to a degree, by the absence of contact when tank and infantry units move together." Obviously, the enemy did fight armored and cavalry units, but usually he either was put in a position where he had to fight or felt that he possessed sufficient strength to defeat the American force. The effective range of the modern 105 mm canister is out to 500 meters. It is large enough to carry a payload capable of incapacitating an advanced squad of 10 men wearing winter gear. The cartridge is fired from standard United States Government military equipment with rifling typically used for firing 105 mm ammunition. The 105 mm canister has a plastic slip band in order to control the spinning of the projectile. There is no fuze on this round. In a preferred embodiment, the canister contains approximately 800-1000 tungsten balls, which are expelled upon muzzle exit.

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Flechettes

Common usage distinguishes between a gunshot wound and a shrapnel wound. More precise usage would term the later a fragment wound. Strictly defined, shrapnel means preformed fragments (the fragments exist already made within the explosive munition). Thus, fragmenrs from a random-fragmentation shell are not shrapnel. Also note that by strict definition, flechettes are shrapnel.

A flechette is a common military missile which is shaped generally similar to a dart or arrow, i.e. it has a relatively long slender body, at one end of which are disposed guiding fins. Flechettes are launched individually toward a target from a launcher having a bore. Flechettes are fin stabilized steel projectiles similar in appearance to arrows. Flechettes have a performance criteria very different from the conventional rifle bullet. Typical modern flechettes are small light weight steel projectiles, and the velocity lost to air resistance is generally 375 fps. per 100 Meters of flight. Unlike rifle bullets, flechettes are not spin stabilized, but use fins to achieve level flight. The flechette's long body looses rigidity on target impact and bends into a hook, often breaking off the fin portion creating an additional wound.

William C. Ingram, of Grand Rapids, Michigan was granted patent 1,340,317 for a Shrapnel-shell on Sept. 18, 1917. This shell was an early embodiment of a flechette warhead.

During the Korean War the Chinese army tactic of human wave attacks against US lines of defence prompted interest in flechette projectiles in single and multiple projectile systems for small arms and antipersonnel (APERS) use. Flechette munitions include projectiles for use in the M16 rifle, CAWS (close assault weapons system), and 12 gage shotgun, as well as the 105mm M101A1/M102 howitzer, 2.75 in. FFAR (folding fin aircraft rocket), and the 70mm Hydra-70 FFAR.

Flechettes are typically designed with the intended target in mind. For example, some flechettes are designed to behave as hardened penetrators to breach harder targets, such as thin armor. Such flechettes are less effective against softer targets because they tend to pass through the target quickly with minimal damage. Other flechettes are designed to damage softer targets by fracturing or bending as they strike the target; however, they are often ineffective against harder targets because of the tendency to fracture or bend upon striking such targets.

In combat situations wherein both harder and softer targets are anticipated, flechettes for each type of target have conventionally been needed. Supplying, storing, and deploying multiple types of flechettes based upon the perceived or anticipated target may lead to logistical difficulties. Other conventional approaches to damaging both harder and softer targets have included the use of other types of penetrators, often having explosive components, which are more expensive to deploy than flechette-based weapons.

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Ground-based air defense gun systems of 20 mm and larger calibers presently in service employ conventional high explosive projectiles for defeating a target. Although high explosive projectiles have good terminal effectiveness against aircraft, their inherent exterior ballistic performance is such as to result in poor hit probability in employment against high speed aircraft. High explosive projectiles contain a fuse mechanism and a high explosive filler. These components are rather voluminous and of low weight, thus adversely restricting the sectional density of the projectile. The resultant ballistic coefficient is such as to induce a high degree of velocity decay as a function of range and correspondingly long time of flight. In employment from ground-based guns against low flying, high speed aircraft, the long time of flight requires very large lead angles and superelevation angles. In the case of advanced ground-support aircraft, these angles are of such magnitudes that even with the use of sophisticated fire control systems the resultant hit probabilities are inadequate.

For ground-based gun fire to be effective, ability to hit the target is a prerequisite. To achieve high hit probability performance against fast-flying enemy aircraft, it is essential to fire projectiles having short times of flight resulting from high projectile velocity. In turn, this reduces the lead angle and superelevation angle requirement.

High velocity projectiles with short times of flight are essential for achievement of high hit probabilities regardless of the degree of sophistication of the fire control system. The desired short times of flight can be attained through the use of sabot-launched subcaliber projectiles having a high muzzle velocity. Furthermore, in order to minimize velocity loss subsequent to launch, the subcaliber projectiles should have a high sectional density, i.e., should consist of a high density material, such as a tungsten alloy for example, having a density of approximately 16 to 19 g/cm.sup.3. These features and related exterior ballistic characteristics are found in advanced discarding-sabot, armor-piercing projectiles described in that patent.

However, while providing the desired hit probabilities, the terminal effectiveness of this type of ammunition against aircraft-type targets is unsatisfactory. Armor-piercing projectiles are of limited terminal effectiveness against soft targets such as high speed aircraft in that the projectile can hit the target causing superficial damage without destroying it.

Owing to the configuration of the flechette, they are difficult to launch from a launcher having a bore. Specifically, the guiding fins of the flechette define a diameter which extends well beyond the diameter of the body of the flechette. Thus, the diameter of the launcher bore must be no smaller than that of a circle defined by the diameter of the guiding fins. Otherwise, the flechette will not fit through the bore. The diameter of the bore is generally far greater than that of the body of the flechette, and so a sabot is used to retain the flechette within the bore.

A sabot, or shoe, comprises at least two pieces of a hard material placed over the exterior of a front portion of the body of the flechette as a covering before the flechette is launched. The interior of the sabot conforms to the shape of the exterior of the body of

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the flechette. The exterior of the sabot generally conforms to the shape of the interior of the bore, and has a diameter greater than that of the guiding fins. The rear end of the sabot, together with the rear portion of the flechette including the guiding fins, is encased within a cartridge which serves to hold the sabot and flechette together. Additionally, the cartridge will retain therein gunpowder or other propellant with which the flechette is launched from the bore.

The front end of the sabot conventionally is configured aerodynamically, so that once the flechette/sabot assembly leaves the muzzle of the launcher, the sabot is aerodynamically peeled away from the flechette, thereby permitting the flechette to fly toward its target unfettered by the sabot. The sabot, having served its purpose, falls to the ground. A common configuration of the front end of a sabot is that of a cup, with the rim of the cup at the front end of the sabot, and the bottom of the cup toward the rear thereof. The pressure of the air on the bottom of the cup after launching peels the sabot away from the flechette.

Conventional sabots are made of a hard and inelastic material, such as, for example, fiberglass-reinforced plastic, and so generally are extremely rigid. This is considered necessary, so that the sabot will not dissipate the propulsive energy applied to its rear end during launching. A problem arises with the use of a sabot, namely retaining the sabot in place with respect to the flechette during launching. Since the force applied to the sabot/flechette assembly during launching is directed axially thereto, and much of that force is applied to the sabot, the sabot tends to slip off the flechette. To counteract such a tendency, a radial force is exerted between the flechette and the sabot, thereby holding the sabot in place. In some applications, this is accomplished by providing a slight tapering at the rear of the sabot. When the propulsive force is applied to this tapering, a portion of the (axial) propulsive force is translated into a radially inward retaining force, tending to retain the sabot in place about the flechette.

This tapering has a disadvantage, since it serves to dissipate a portion of the propulsive force. Additionally, forcing the rigid sabot against the flechette leaves a small space between the exterior of the sabot and the interior of the bore, through which a portion of the propulsive force may leak. Also, the sabot has an exterior diameter which is equal to or slightly less than that of the bore. Any difference in dimension leaves a small space between the sabot and the interior surface of the bore, through which a portion of the propulsive force may dissipate. Furthermore, the existence of the small space between the sabot and the bore means that the sabot is not retained tightly within the bore, and so has a slight freedom to separate while in the bore. Any separation of the pieces of the sabot is also extremely undesirable, since it will further permit some dissipation of the propulsive force therebetween, and will permit the sabot to release the flechette.

In some applications, a retaining member, or obturator, such as a rubber band, is affixed about the sabot, to exert a radially inward retaining force. The obturator also serves to fill the small space between the sabot and the interior of the bore, and so seals off the bore from any leaking of propulsive energy about the sabot, or between its pieces. The use of

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an additional retaining member is also a disadvantage, however, since it increases the cost of the assembly, and adds to the labor involved in its construction.

It is known to use a plastic sabot to surround a flechette and to have the barrel rifling only engrave the sabot, which transfers the rotation to the flechette by mechanical engagement with the fins of the flechette, instead of by a friction grip, and therefore a low coefficient of friction material can be used for the sabot with a resulting low friction loss in the barrel. One consequence of using a flechette however is that the combined weight of the sabot and flechette is very light when compared to a conventional bullet of the same diameter and length so that a special automatic gun must be used to function with the reduced impulse. A further problem with all sabot launched projectiles is that since the sabot and projectile exit from the barrel at the same velocity, the energy of each is determined by their relative mass to one another. The heavier the sabot is in relation to the projectile, the greater is the percentage of lost energy, since the sabot serves no useful purpose as a projectile. In the prior art, the body diameter (shaft) of a flechette is small in comparison to the sabot diameter, with a resulting large proportion of mass and energy in the sabot, so that the flechette gets a relatively small amount of the total energy and is therefore the least efficient of the sabot type projectiles.

 

Painting and Marking

All projectiles are painted, both as a means of ready identification and as a rust preventative. The basic colors used for many years were olive drab (OD) for high-

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explosive rounds, gray for chemical rounds, blue for practice rounds, and black for drill rounds. A system of contrasting color markings or bands in addition to the basic color has also been used to identify the particular type of high explosive or chemical used as a filler. Color coding of recently produced projectiles is somewhat different. For example, illuminating and smoke rounds are no longer painted gray, the basic color for chemical shells. Illuminating rounds are now painted basically white or olive drab, and the smoke rounds are painted green. The basic color for dummy ammunition has been changed to bronze. Projectiles containing high explosive TNT Amatol, etc.) are painted yellow. Projectiles containing chemicals (gas or smoke) are painted blue-gray. Projectiles containing low explosives (black powder) are painted red. Projectiles are also stenciled to show the caliber, type of cannon used in, ammunition lot number, kind of filling, etc.

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