Journal of Criminal Law and Criminology

Volume 60 | Issue 3 Article 14

1970

Bullet Ricochet From Metal PlatesMohan Jauhari

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Recommended CitationMohan Jauhari, Bullet Ricochet From Metal Plates, 60 J. Crim. L. Criminology & Police Sci. 387 (1969)

THE JOURNAL Or CnIMINAL LAw, CREIINOLOGY AND POLICE SCIENCE Vol. 60, No. 3Copyright © 1969 by Northwestern University School of Law Printed in U.S.A.

BULLET RICOCHET FROM METAL PLATES

MOHAN JAUHARI

Mohan Jaubari, M.Sc., is Assistant Director of the Central Forensic Science Laboratory, Govern-ment of India, Calcutta, where he serves as head of the Ballistics Division. For the last nine yearshe has been engaged in research in the field of Forensic Ballistics, in addition to his identificationwork in firearms and his service as an expert witness throughout India. Mr. Jauhari is co-author ofa booklet "Firearms and Firearm Injuries" published by the Government of India for police andmedical officers, and is an active member of the Indian Academy of Forensic Science. In 1968 he touredthe United States on a public safety study-training program sponsored by the Agency for Interna-tional Development, Washington, D.C.-rEmTo.

When a bullet strikes a target of sufficientsolidarity at low angle it may, while maintainingits integrity, be deflected from its original path asa result of impact and travel in a direction quitedifferent from its original one. Such a deflection ofa bullet constitutes a true ricochet.

The Encyclopaedia Britannica attributes thediscovery of ricochet fire, in which the shot afterstriking the ground at small angle described forthe remainder of its course a series of leaps andfalls, to Vauban. In old days this type of fire hadthe greatest influence both on sieges and on opera-tions in the field. Due to the insufficient mobilityof field artillery before Napoleon's time reliancewas placed principally on the ricochet of roundshot. With the development of artillery andconsequent improvement in its mobility ricochetfire was used more and more sparingly and finallydriven into oblivion with the appearence ofexplosive filled shells. In siege warfare also thedevelopment and perfection of high angle firecompletely obviated the necessity of ricochet fire.However, ricochet fire with delayed action fuseswas resorted to even in World War II to obtainair bursts after initial impact. In modem warfarericochet fire is more or less a dead issue. Themention of ricochet is nowadays made only inconnection with small arm projectiles.

According to Hatcher richochet fire used inold days (round cannon balls fired from smoothbore cannons) was about as accurate as directfire. This has ceased to be so with modem smallarm projectiles due to their elongated shape, highvelocity, and spin. He regards the phenomenon ofbullet ricochet as essentially one of low ratherthan high velocity because a bullet travelling at

1HATCHER, JuRy, Am WELLER, FmARMs INVESTr-GATION, IDENTIFICATION AND EVIDENCE. The StackpoleCompany, pp 422-423, 1957.

high velocity usually breaks on striking a hardtarget.

Practical experience in the field of ForensicBallistics shows that the phenomenon of bulletricochet is not very well understood even amongstthe experts. This is so inspite of the fact that thisphenomenon plays an important part in criminalinvestigation. Ricochet marks are very often en-countered on targets of diverse nature in shootingincidents and deserve due consideration in crimescene reconstruction. The following are some of theaspects of bullet ricochet that deserve mention andcareful consideration:

a. Critical angle for ricochet.b. Relation between the angle of incidence and

ricochet.c. Relation between the plane of incidence and

ricochet.d. Bullet stability after ricochet.e. Bullet lethality after ricochet.A review of literature shows complete lack of

data concerning critical angles for ricochet forbullets loaded in common cartridges when firedagainst targets usually encountered in crimes.There is also no clear understanding regarding therelation between the angle of incidence andricochet. Equally deficient is information on theother aspects mentioned above. It is, therefore,necessary to carry out a large number of controlexperiments with common cartridges and targetsfrequently involved in crimes. An investigationof this nature is not only expected to help inunderstanding of the phenomenon of bullet ricochetin general but also to provide useful data in respectof the cartridges and the targets used for experi-ments. The investigation has, therefore, beencarried out with different cartridges and targets,and the results obtained in respect of some of themetallic targets have been reported in the presentpaper.

MOHAN JA UI1ARI[

DEFINITIONS AND ABBREVIATIONS

Referring to Diagram I, let OX, OY, and OZ be aset of three mutually perpendicular axes meetingin origin 0. Let the target be represented by thevertical plane YOZ. The plane XOY is anothervertical plane perpendicular to the target plane.Let the horizontal plane XOZ be the plane offire i.e. one containing the line of fire.

y

I -

DIAGRAm I

iLet a bullet fired along PI strike the target atI and ricochet in the direction IR where R is thepoint of intersection of IR with the plane XOY.For generality it is assumed that the line IR isnot contained in the plane of fire.

The following terms may now be defined:Plane of incidence is a plane perpendicular to thetarget plane and containing the line of fire. Itis represented here by the plane XOZ and isthe same as the plane of fire.Plane of ricochet is a plane perpendicular to thetarget plane and containing the line along whichthe bullet travels immediately after ricochet. Itis represented here by the plane IRR". Whenthe line along which the bullet travels afterricochet lies in the plane of incidence, theplane of incidence and ricochet coincide.

Angle of incidence is the acute angle between theline of fire and the line into which the incidenceand the target plane intersect. It is representedhere by ZPIZ.Angle of ricochet is the projection on the incidenceplane of the acute angle between the line alongwhich the bullet travels immediately afterricochet and the line into which the ricochet andtarget plane intersect. It is represented here byZR'IO.Critical angle for ricochet is the maximum angleof incidence at which the bullet ricochets. Oncethe angle of incidence exceeds this value thebullet fails to ricochet by either disintegratingor penetrating the target.The following abbreviations will be used:i: Angle of incidence.r: Angle of ricochet.r. : Critical angle for ricochet.L: Lead or unjacketted.MJ: Metal jacketted.S: Stable.US: Unstable.P: Penetration.NP: No penetration.

MATERIALS AND METHODS

The choice of the targets was governed by thefrequency of their occurrence in day to day lifeand easy availability in some suitable formcharacterizing uniformity. Metal plates of uniformthickness were, therefore, chosen for experimenta-tion. The following are the targets which were usedfor collecting bullet ricochet data:

a. Aluminium plates measuring 1' x 1' xand 1 ' x 6"-

b. Brass plates with the same dimensions.c. Steel plates with the same dimensions.Firearms of typical calibers frequently involved

in crimes were selected for conducting experi-mental firing. The cartridges chosen were essen-tially low velocity cartridges. This was purposelydone for reasons of safety during experiments aswell as due to the fact that a high velocity bulletgenerally disintegrated on striking a hard metallictarget like the ones considered here. The firearmsand the ammunition together with their ballisticdata of interest in relation to the present investi-gation are given in table 1.

The experimental arrangement is shown infigure 1. The plane YOZ was replaced by thetarget (refer diagram I) which was held firmly in a

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BULLET RICOCHET FROM METAL PLATES

Table 1

Bullet InstrumentalFirearm Ammunition Bullet Weight in velocity in

Type grains. ft./sec

.22 Rifle No. 2, Mk 4, S. No. 6278 .22 Long Rifle, K.F. L 40 1000

.38 W & S Revolver, S. No. 24706 .38 Ball, Mk 2, K.F. MJ 178 600

.45 Colt Pistol, M1911, S. No. 22383 .45 ACP, Rem-Umc. MJ 230 800

vertical plane on the horizontal floor of a steellined bullet recovery box measuring 8' x %2' x

%,. This was achieved by designing a woodenframe with a flat wooden base attached at rightangles to it. The target was put in the frame andthe base of the frame was firmly secured to thefloor of the bullet recovery box by putting heavyweights on the base and providing checks at itscorners. The firmness of the base was confirmed byfiring a few rounds on the target before starting theexperiment and ensuring that the frame did notbudge from its predetermined position.

The line PI was made to coincide with the lineof fire by holding the firearm in a vice with itsaxis horizontal and plane of symmetry vertical.The vice was kept outside the bullet recovery box

on a table and secured firmly to it by nuts andbolts. The distance between the muzzle of thefirearm and the target was kept to a minimum thatwould stabilize the bullet before striking thetarget. The stability of the bullet was checked byfirst firing on a paper screen kept at the distanceof the target and seeing that no keyholes wereproduced on the screen.

To fix the angle of incidence a long rod fittingsnugly into the barrel of the firearm was insertedin the muzzle and extended upto the target. Theangle of incidence was then measured by a pro-tractor in the horizontal plane. The angle of inci-dence was changed by rotating the wooden frameif and when desired.

The plane XOY was replaced by a deal wood

FiGuRE 1. Experimental Arrangement

1969]

MOHAN JA UHARI

board 1" in thickness. The deal board was held ina vertical plane near the target and at right anglesto it. The board was meant to record the point ofimpact R of the bullet after ricochet thus facilitat-ing the measurement of the angle of ricochet andstudy bullet penetration after ricochet. The boardwas kept very near the target so that the bulletduring its passage from the target to the board didnot drop significantly due to gravity and also didnot deviate from its true direction of ricochet dueto possible instability. In such circumstances theline IR represented the true direction of ricochet.Once the position of point R was ascertained onecould derive information about the plane ofricochet in relation to the plane of incidence.Whenever I and R were found to be at the samevertical height above the floor of the bullet re-covery box it was inferred that the plane ofincidence and ricochet were the same. Any move-ment of the point R upwards or downwards indi-cated otherwise.

Bullets were fired at different angles of incidenceand the position of point R was recorded in addi-tion to observations on penetration in deal board.The angle of ricochet (r) was calculated with thehelp of the simple relation

OR.'Zr = tan,-

I0

The angle of incidence was increased in steps of150 starting from 15'. The observations betweenthe incidence angle at which the bullet failed toricochet and the one preceding it were, however,taken at steps of 5' with a view to determine thecritical angle for ricochet within close limits. Thecritical angle thus lay between the maximum angleof incidence for which the ricochet was observedand the minimum angle of incidence for which thebullet failed to ricochet by either disintegratingor penetrating the target. The appearance of thebullet holes on the deal board provided a clearpicture of bullet stability after ricochet. This wasfurther checked by interposing a paper screenbetween the deal board and the target and observ-ing bullet holes on the screen.

BULLET RICOCHET DATA

The tables 2, 3 and 4 give bullet ricochet datain respect of the targets and ammunition used forexperiments. The tables are self explanatory.

RESULTS AND DIscussIoN

A review of bullet ricochet data shows that thebullets became unstable after ricochet. Duringthe course of experiments it was observed that thebullets hit the deal board in all possible ways afterricochet i.e. sideways, base forward, etc. To ensurethat this instability was due to ricochet and notdue to impact on the deal board, paper screenswere interposed in the bullet path from the targetto the deal board. The holes on the paper screensconfirmed that the bullets were indeed unstableafter ricochet. The bullets did not appear to beunstable when the angle of incidence was 5' orless (data not reported here). The cartridges usedfor the present investigation are loaded with baseheavy spin stabilized elongated bullets. Thesebullets are likely to become unstable on impact.However, at extremely small angles of incidencethe contact between the bullet and the targetcould be soft enough so as not to produce anyobservable instability under the experimentalconditions. This was very probably the reason forthe lack of instability exhibited at these angles.

An examination of the fired bullets revealedthat they were invariably deformed. The amountand the nature of deformation depends uponseveral factors such as bullet material, target,angle of incidence, velocity, etc. A combination ofhard target, soft bullet material and high velocityis likely to promote greater deformation assumingother factors to be constant. The bullets gotflattened on the sides which bore the brunt ofimpact. In one instance in case of .22 lead bulletwhen fired on X" steel plate at 30' incidence thisflattening led to the formation of a sharp edge.The hole in the deal board in this particular casewas found in the shape of a vertical thin slit. Itcan be very well visualized that such bullets arelikely to create wounds which may easily bemistaken as incised wounds. This will be evenmore likely if the bullet fails to lodge itself in thebody. Atypical wounds of entrance are thereforeexpected from ricocheting bullets.

As a bullet not only becomes unstable on ac-count of ricochet but also is deformed, it is clearthat it is bound to have an erratic path afterricochet and lose velocity at a rapid rate. Thebullet initially lost energy by striking a targetwhich was relatively at rest, and this loss wasfurther accentuated on account of its deformationand instability. The conclusion that the woundingpower and the lethal range of a bullet is likely to

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BULLET RICOCHET FROM METAL PLATES

Table 2Firearm: .22 Rifle No. 2, Mk 4, S. No. 6278Ammunition: .22 Long Rifle, K.F.

Ricochet Bullet Bullet pene-

Target d rgn r n pation to stability tration in 11 ro indegrees degrees ltin after deal board degrees Remarks

Incidence ricochet after ricochetplane

Aluminum 10 6 Same US P 10-15X6" 1 . .. Bullet disintegrates and a por-

tion passes through the tar-get creating a hole.

Aluminum 15 2 Same US P 30-3530 3 Same US NP35 - . Bullet disintegrates without

creating a hole in the target.

Brass 15 3 Same US P 25-30H6" 20 8 Same US P

25 6 Same US P30 - .. Bullet disintegrates without

creating a hole in the target.

Brass 15 3 Same US P 20-2520 2 Same US P25 - Bullet disintegrates without

creating a hole in the tar-get.

Steel 15 2 Same US P 30-3536' 30 3 Same US NP

35 - Bullet disintegrates without

creating a hole in the target.

Steel 15 Almost Same US P 30-35Nn zero

30 1 Same US P35 - Bullet disintegrates without

creating a hole in the target.

be considerably reduced after ricochet seemsinevitable.

The bullets of each one of the cartridges used forexperiments are capable of penetrating severalboards of 1" thick deal wood when fired directly.However, it will be noted (see tables 2, 3 and 4)that in many instances especially at higher anglesof incidence the bullets failed to penetrate evenone board after ricochet; at smaller angles ofincidence they could penetrate one board. Thebullets were, however, unstable at both the higherand the lower angles of incidence. It is true thatinstability and deformation affect penetration to agreat extent but it also appears that the loss of

velocity and hence energy was also responsible forthe loss of penetration. At higher angles of inci-dence the impact is expected to be harder ascompared to that at lower angles, and thus abullet is likely to suffer more loss of energy athigher than at lower angles of incidence.

The angles of ricochet reported represent anaverage of a number of observations taken at eachangle of incidence. A fair degree of consistency wasobserved between these values. Further each singlevalue of the angle of ricochet was less than thecorresponding angle of incidence. The differencebetween the angle of ricochet and the correspond-ing angle of incidence was also several degrees.

19691

MOHAN JA UHAR[

Table 3Firearm: W & S Revolver, S. No. 24706Ammunition: .38 Ball, Mk 2, K.F.

Target

Aluminum

X6"

i indegrees

15

2025

r indegrees

510

Ricochetplane in

relation toincidence

plane

SameSame

Aluminum 15 4 SameY8" 30 7 Same

35 8 Same40 - -

Brass

6"

SameSameSameSame

Bulletstability

afterricochet

USUS

USUSUS

UsUSUSUS

Bullet pene-tration in 11deal board

afterricochet

reindegrees

20-25

35-40

60-65

Remarks

Bullet disintegrates and a por-tion passes through the tar-get creating a hole.

Bullet disintegrates withoutcreating a hole in the target.

Bullet disintegrates withoutcreating a hole in the target.

Brass 15 4 Same US NP 35-40Yf 30 8 Same US NP

35 9 Same US NP40 - -- - Bullet disintegrates without

creating a hole in the target.

Steel 15 3 Same US NP 50-55 -

36" 30 7 Same US NP45 15 Same US NP

50 17 Same US NP55 - Bullet disintegrates without

creating a hole in the target.

Steel 15 3 Same US NP 50-553" 30 6 Same US NP

45 8 Same US NP50 9 Same US NP55 - Bullet disintegrates without

creating a hole in the target.

It is, therefore, fair to conclude that the angle ofricochet is less than the angle of incidence. At thesame time it can also be seen that the amounts bywhich the angles of ricochet fall short of the cor-responding angles of incidence do not follow anysystematic pattern. It has been stated above thatinstability and deformation led the bullet to takean erratic path after ricochet. However, it isunlikely to exhibit this erratic behavior in close

proximity of the target and is likely to travel in itstrue direction of ricochet. The drop due to gravityis also insignificant within this small distance.These considerations were mainly responsible forkeeping the path of the bullet from the tarAet tothe deal board after ricochet to a minimum. Thereduction of this path at the same time reducedthe accuracy of measurement of the angle ofricochet. This can be visualized by referring to the

-1

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BULLET RICOCHET FROM METAL PLATES

Table 4Firearm: .45 Colt Pistol, M1911, S. No. 22383Ammunition: .45 ACP, Rem-Umc.

Ricochet Bullet Bullet pene-plane sb traionin1R

Target i in rin relation to t deal board dreindegrees degrees incidence r after egreesplane ricochet ricochet

Aluminium 10 7 Same US P 10-15X6, 15 - Bullet penetrates the target.

Aluminium 15 5 Same US P 25-30." 20 8 Same US P

25 12 Same US P30 - Bullet penetrates the target.

Brass 15 11 Same US P 25-3020 12 Same US P25 19 Same US NP30 - Bullet penetrates the target.

Brass 15 7 Same US P 50-55 -Y1 30 12 Same US P

45 13 Same US NP50 16 Same US NP55 - . Bullet disintegrates without

creating a hole in the target.

Steel 15 7 Same US P 30-35346' 30 10 Same US P Bullet hole in the target with-

out the passage of bullet.35 - Bullet penetrates the target.

Steel 1s 1 Same US P 30-35/1" 30 3 Same US P

35 - Bullet disintegrates withoutcreating a hole in the target.

equation used for the calculation of the angle ofricochet. The size of the bullet recovery box, whichcould not be dispensed due to reasons of safety,also imposed restriction on this distance. The lengthof the bullet path from the target to the dealboard was in fact the best compromise after takingthese factors into consideration. Thus the rela-tionship that the angle of ricochet is less than theangle of incidence holds good for the true directionof ricochet along which the bullet travels imme-diately after ricochet and may not hold if, for thecalculation of the angle of ricochet, the point ofimpact on deal board is recorded at some con-siderable distance from the target when theerratic behavior of the bullet stemming out of itsinstability and deformation comes into play. It,therefore, appears that the unpredictability of

ricochets is inter alia due to the erratic path takenby the bullet on account of instability and de-formation.

The plane of ricochet was found to be the sameas the plane of incidence. In the experimental set upadopted here any deviation of the bullet to theleft or to the right in the horizontal plane due tospin is likely to be absorbed in the angle of ricochet.If, however, the target is kept horizontal, devia-tion on account of spin, if any, may exhibit itselfin the form of a plane of ricochet different fromthe plane of incidence. It is proposed to investigatethis aspect in the future. Further if the plane ofricochet is determined by recording the point ofimpact on the deal board at sufficiently largedistance so as to make drop due to gravity signifi-cant the plane of ricochet may again appear to be

19691

MOHAN IA UHARIol

different from that of incidence. The relationshipthat the plane of ricochet is the same as the planeof incidence, therefore, holds good so long as theplane of ricochet is defined with respect to the truedirection of ricochet along which the bullet travels,immediately after ricochet.

The critical angles for ricochet are generallydifferent for different combinations of firearm,ammunition, and the target. These values mayalso be affected to some extent by the manner inwhich the target is held. Thus whereas the valuesgiven here cannot be treated as standard under allexperimental conditions they definitely give a verygood idea of the order of magnitudes involved.

Experiments showed that .22 lead bullets and.38 jacketted bullets could only penetrate alumin-ium targets (X6" & %") and not the other oneswhen "Normal Firing" was undertaken from thesame distance as adopted in ricochet studies. The.45 jacketted bullets could not penetrate brass andsteel targets (%") but could penetrate the othersunder similar conditions. It is obvious that a bulletfails to ricochet by disintgerating on targets whichit is incapable of penetrating. It will fail to ricochetby penetrating or disintegrating on those targetswhich it is capable of penetrating. In some casespenetration and disintegration may simultaneouslyoccur and only a part of the bullet may actuallypass through the hole. A glance at the Remarkscolumn of tables 2, to 4 shows this tohavebappened.When the .45 jacketted bullet was fired on Me"Steel plate at 30' incidence the bullet ricocheted,but at the same time the target gave way and anelongated hole was produced without the passageof bullet (see Figure 2). The phenomenon of bullethole without the passage of bullet may haveinteresting forensic implications,

FIGURE 2. Bullet Hole Without the Passage of theBullet (.45 jacketted bullet against A" steel plate at300 incidence)

The results stated above mostly hold good for

the targets, firearms, and ammunition under theexisting experimental conditions. It is not possible

to make generalizations at this stage when thedata: itself is so meagre. The experimental set upalso offers scope for improvement. It is, however,believed that the present investigation will providethe neccessary ground work and stimulate furtherresearch in this field using many other targets,firearms, and ammunition. Work on these lines is

in progress.

ACKNOWLEDGMENTS

The author wishes to put on record his grateful

thanks to Dr. N. K. Iyengar, Director, CentralForensic Science Laboratory, Govt. of India,

Calcutta for keen interest in the Work, Mr. J. P.

Nigam, Scientific Assistant, State ForensicScience Laboratory, Saugor for providing in-

valuable technical assistance during the course ofhis attachment to the author for training and toMr. R. C. Banerji, Scientific Assistant, CentralForensic Science Laboratory, Govt. of India,Calcutta for photography.

[V61,.,60