silentsniping.pdf

CARTRIDGES FOR SILENCED SNIPING RIFLES

© Anthony G Williams

Substantially rewritten January 2013

The sniper is the most efficient of soldiers. The current military emphasis on firepower, combined with the use ofdeterrent suppressive fire, has seen the number of small arms rounds fired per casualty inflicted rise from severalhundred at the start of this century to tens if not hundreds of thousands in modern high-intensity conflicts. Through allthis, snipers have maintained a rate of approximately 1.3 rounds per casualty.

The lethal effectiveness of snipers also makes them the most unpopular of soldiers with their adversaries. Detection of asniper usually results in a mortar attack if not a comprehensive artillery shoot, so snipers have to be experts inconcealment as well as crack shots. They also have to be prepared to change position rapidly as soon as they feel thattheir position might have been spotted.

Most sniping rifles are chambered for the standard military cartridge, currently usually the 7.62 x 51 NATO or 7.62 x 54 RRussian depending on historical allegiance. These are not ideal because a heavier bullet at a higher muzzle velocitywould ensure better long-range accuracy, so specialist rifles are available with more powerful cartridges such as the.300" Winchester Magnum and the .338" Lapua. Some rifles go even further, being chambered for rounds of calibres up

to the .50" Browning heavy machine gun cartridge. These are described in THIS article.

All of these rifles have a major disadvantage from the sniper's point of view in that they are very obvious in use. Themuzzle report can be heard at great distances and although this problem is increasingly being tackled by fitting a soundsuppressor, the sharp crack of a supersonic bullet still gives clear warning to the enemy that they are under attack.There has therefore been a continuing interest in a genuinely silent sniping rifle for covert operations, and there is awider choice now than has ever existed before.

The problem is that a silent rifle has to generate a muzzle velocity below the speed of sound, which is at around 320m/sec (1,050 fps) depending on altitude and air temperature. This is in the realm of pistol rather than rifle cartridges so it

is no surprise that one of the first and best known of such weapons used such a cartridge. This was the De Lisle

Carbine, developed for British special forces in World War 2, which consisted of a Lee Enfield bolt action rifle chamberedfor the standard .45" Auto from the Colt 1911 pistol (11.5 x 23 in metric) and fitted with an 210mm barrel and a massivesuppressor. Initial examples used the standard Lee-Enfield stock but a paratroop version with a folding stock was alsoproduced. The problem with the De Lisle was that although it was reportedly accurate to over 300m, the velocity ofaround 260 m/sec combined with a relatively light (230 grain / 14.9 g) round-nosed bullet which lost velocity relativelyquickly resulted in a rainbow-shaped trajectory at long range, making accurate range estimation crucial.

The next development along these lines went some way to solving the problem. This was an American bolt action rifle,fitted with a target barrel, a silencer and a telescopic sight, which saw experimental use in Vietnam. It was based around

a new cartridge, the .458 x 1.5" Barnes (actually 11.6 x 33 B), which was essentially a shortened .458" Winchester biggame round, firing the usual 500 grain (32.4 g) bullet at just below the speed of sound. It was apparently not entirelysuccessful, largely because the bulk and weight caused by the long, heavy target barrel didn't endear it to the troops.

Even this was not the ultimate answer as the bullet was still round-nosed and therefore quickly lost velocity andeffectiveness at long range. This prompted the development of cartridges using very heavy, pointed, boat-tailed bullets ofexcellent shape to minimise the velocity loss. Initially these were modified loadings of existing rifle rounds and suchloadings are still available in all standard military rifle calibres, as they have some utility where the users want to carryonly one weapon for both covert and open use. However, these are not very efficient: the small calibres limit the bulletweight which can be used before the rifling can no longer stabilise the bullet's flight, while the cartridges cases are fartoo big for the small quantity of propellant needed to reach subsonic velocity.

As a result, a new breed of specialised subsonic rounds has arisen in the past few decades. These can only be used inpurpose-designed rifles, usually fitted with short barrels and a large suppressor. They are designed for maximumefficiency in the role, so have relative large calibres and use small cartridge cases to fire the heaviest practicable bullets.The smaller versions are intended for use in suitably modified military rifles which may also feature selective fire (thecapability for automatic firing), the larger ones for use in bolt-action rifles. Some of the cartridges are also available withsupersonic loadings (for use with or without the suppressor) so that users can be more effectively equipped for whencovert use is not needed.

One of the first, and certainly the most prolific, manufacturers of specialist subsonic rounds is SSK Industries of the

USA, who produce the Whisper range of ammunition. These include 6, 6.5, 7, 7.62 (.300 Whisper), and 8.6 mm (.338

Untitled Document http://www.quarry.nildram.co.uk/silcart.html

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Whisper II) rounds, all using cartridge cases with the same diameter as the 5.56 x 45 but just 35-36 mm long so theycan be loaded with longer bullets while keeping within the same maximum round length. This enables them to bechambered in rebarrelled versions of the standard M16 assault rifle, and they can even use the 5.56 mm magazines.SSK also makes subsonic loadings of the 7.63 x 25 (.30 Mauser) and 7.65 x 21 (.30 Luger) cartridges, marketed as the

Mini-Whisper and Micro-Whisper respectively, with pointed heavy bullets making them too long to be used in the

pistols. Other cartridges are based on the 7.62 x 51 NATO case, but shortened and again in various calibres: .302, .338

(Whisper I) .375 and .416 Whispers, the last of these (which has so far evaded my collection) being virtually straight-cased. These can be used in modified 7.62 mm rifles such as the AR-10 family, or when fitted with shorter bullets to keepthe same overall length as the 5.56 x 45 can be used in an M16 with more extensive modifications and different

magazines. Finally, even larger rounds have been developed: the .458, .500 and .510 Whispers, based on the .458Winchester Magnum, .460 Weatherby Magnum and .338 Lapua Magnum cases respectively.

The smallerexamples areunlikely to havemuch military utilityso this article willfocus on those of7.62+ mm (.30+inch) calibreintended for use inmilitary rifles. Thesmallest of thesewas the first tocome to notice andis probably themost popular by along way; the .30"Whisper (now

known as the .300

Whisper), whichuses a .221"Remington Fireballcartridge neckedout to 7.62 mmcalibre to take a210 grain (13.6 g)boat-tailed spitzermatch bullet. Thishas proved sosuccessful that ithas prompted verysimilardevelopments byothermanufacturers.The first was forthe Heckler & KochSL9 SDsuppressed rifle;

the 7.62 x 37 HK,produced by BAESystems RadwayGreen ammunitionplant in around2000. It is unclearwhether or not thisrifle achieved anysales, and theammunition is nolonger inproduction. In the


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past couple ofyears three othervery similar roundshave emerged: the

7.62 x 37 Musangfrom thePhilippines (whichhas also yet to finda place in mycollection), the

AAC 300 Blackout

and the 7.62 x 40

Wilson Tactical,both from the USA.The Blackout is astraight copy of the.300 Whisper, themain differencebeing that it isSAAMI registeredand the focus ismore on thesupersonicloadings, which area close match forthe old 7.62 x 39Kalashnikovrounds. TheWilson round isoptimised forsupersonicloadings and isincluded here onlyfor comparisonpurposes.

The main US rival to SSK is Teppo Jutsu, which offers three options. The .30 HRT is essentially a 6.8 x 43 Remingtoncase modified to 7.62 x 41. It therefore has a case diameter intermediate between the 5.56 mm and 7.62 mm, but can beused in suitably modified AR-15 (M16) rifles. This is not a specialised subsonic round because the emphasis is verymuch on the supersonic loadings, but it is also offered loaded with a 15.6 g (240 grain) bullet in a subsonic loading. The

.338 Spectre uses the same case shortened to 32 mm, the .458 SOCOM is a multi-purpose (supersonic and subsonic)

cartridge small enough to fit into modified M16 rifles while and the .500 Phantom can be used in modified 7.62 mm rifleswhen loaded with shorter bullets than the A-MAX shown below. It is even available with a saboted .30 cal bullet at 3,200

fps (975 m/s)! More details and photos of the Teppo Jutsu range are HERE.


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One Americanoddity is the

.460 Alliance,very much inthe samemould as thebig-borecartridgesdeveloped forthe AR-15 asdescribed

HERE.However, it isintended formodifiedKalashnikovAK/AKMpattern rifles.It is currentlyonly availablein supersonicloadings, buthas clearpotential for aheavy-bulletsubsonicdevelopment.

TheAmericans arenot the onlyonesinterested insubsonicrounds as theFrenchdeveloped the

ANTHIS rifle,based on anERMAweapon usinga STOPSONsoundsuppressor.The cartridge,based on the.460"Weatherbycase, appearsto bedimensionallyidentical tothe .50"Whisper andwas in factmade inAmerica byA-Square.Any .50"Browningmachine gunbullet could


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be used.

The mostprolificdevelopers ofsubsonicammunitionafter theAmericanshave been theRussians. Thebest-knownexample is the

9 x 39,developed bynecking-upthe 7.62 x 39case after aheavy-bulletloading of thatcase provedunsatisfactory.It is in use in aspecialisedsuppressedrifle (the VSS)but theeffectivenessof the heavybullet at shortrange hasalso led to itsadoption insomeunsuppressedcompactassault riflesfor urbanfighting, suchas theOTs-14, 9A-91and SR3MVikhr. Russiahas alsointroduced the

12.7mm

Vychlop,using a 12.7 x55 straightrimless casewhich issimilar to the.510 Whisper.This isavailable inseveralsubsonicloadings foruse in theVSSKsuppressedrifle. More


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recently,supersonicloadings havebeendeveloped foruse in theASh-12selective-fireassault rifle.

MODERN CARTRIDGES FOR SILENCED RIFLES

Designation Metric designationRim / bodydiameter mm

Subsonic bullet weightgrains (grams)

Sectional Density

.300 Whisper 7.62 x 35 9.5 / 9.5 240 (15.6) 0.365

AAC .300 BLK 7.62 x 35 9.5 / 9.5 220 (14.25) 0.333

7.62 mm HK 7.62 x 37 9.5 / 9.5 200 (13) 0.304

.338 Whisper II 8.6 x 36 9.5 / 9.5 200 (13) 0.250

.338 Spectre 8.6 x 32 10.6 / 10.6 300 (19.4) 0.373

.375 Whisper 9.5 x 37 12.0 / 12.0 300 (19.4) 0.306

.458 SOCOM 11.6 x 40 RB 12.0 / 13.5 600 (39) 0.412

.302 Whisper 7.62 x 38 12.0 / 12.0 240 (15.6) 0.365

.338 Whisper I 8.6 x 38 12.0 / 12.0 300 (19.4) 0.373

9 x 39 Russian 9 x 39 11.3 / 11.3 250 (16.2) 0.284

.458 Whisper 11.6 x 45 B 13.5 / 13.5 500-600 (32-39) 0.338-0.412

.500 Phantom 12.7 x 39 RB 13.3 / 15.6 660-750 (43-48) 0.368-0.410

.500 Whisper 12.7 x 57 B 14.6 / 14.7 660-750 (43-48) 0.368-0.410

.510 Whisper 12.7 x 48 14.7 / 14.7 660-750 (43-48) 0.368-0.410

12.5 mm Vychlop 12.7 x 55 14.8 / 14.8 710-1,170 (46-76) 0.393-0.650

NB: The Sectional Density (SD: a function of the bullet weight and calibre) is multiplied by a form factor derived from theshape of the bullet in order to obtain the Ballistic Coefficient (BC). The higher the ballistic coefficient, the better thevelocity retention and therefore the greater the effectiveness at long range. The SD gives an indication of the potential forbarrier penetration and long-range performance, when comparing bullets of similar shape.

REFERENCES

IHS Jane's Weapons: Ammunition (2013-2014 edition)

Military Small Arms of the 20th Century (Hogg & Weeks)

Cartridges of the World (Barnes)

The Cartridge Researcher, January 1997 (item by Barlerin & Regenstreif)

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