Bullet performance and wounding capabilities

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This is another of those subjects surrounded by myth and misinformation. In many ways, this is understandable as the number of factors influencing how a bullet reacts on entering a human body is so diverse as to make a scientific study of the subject virtually impossible.

If the body were made uniformly from a material of constant density, it would be extremely simple to simulate the effects of a bullet. The body is, however, full of voids with a hard bone skeleton and is associated cartilaginous materials. The effects of a bullet hitting the thigh bone and muscle will be completely different to one striking the chest area which has little muscle or hard bony material.

In an attempt to obtain some meaningful results for the wounding capabilities for handgun ammunition, the US War Department constituted a board, in 1904, consisting of Col. T. Thompson (the inventor of the Thompson sub-machine gun) and Col. Louis A. La Garde. This board was to conduct a series of tests to determine the stopping power and shock effect necessary for a service pistol. The results of the board' s experiments were fully described in Col. La Garde' s book, Gunshot Injuries.

This is one of the most important investigations undertaken into the wounding effects of handgun bullets, as it consisted of controlled shots into human cadavers.

Many of the calibres used in the tests are no longer popular, but the basic findings, that it is the bullet 's cross-sectional area and nose shape rather than the speed, which are the all-important considerations in the wounding capabilities of a bullet, still hold today.

In the tests, the cadavers were suspended by the neck whilst being shot. The quantity of shock to the cadaver by being struck by the bullet was estimated by the disturbance to the body. The bodies were also dissected to determine the degree of tissue damage.

The ammunition used during these tests was as follows:

• 0.38" super ACP, full jacket and soft point;

• 0.45" long Colt revolver, plain lead and hollow point;

• 0.455" revolver, 'man stopper ' (a flat-nosed bullet with a very large cup-shaped hollow point);

The results were quite interesting in that the higher- velocity small- calibre bullets, even when they had a soft or hollow point, caused almost no shocking power at all. The shocking power was, in fact, found to be proportional to the cross-sectional area of the bullet with velocity being only of secondary importance.

These tests were of course on cadavers which could not give any indication of the propensity for a round to incapacitate the subject. To investigate this aspect, a series of rapid firing tests were carried out on live steers in an abattoir. A series of up to 10 shots were fired into the lung or intestinal area of the animal after which it was humanely dispatched.

Once again, the smaller-calibre bullets had virtually no effect on the animals at all. The 0.38" calibre bullets had little effect until the sixth or seventh shot had been fired. Only the 0.45" and above calibre bullets were found to have any appreciable effect, on the first shot.

This type of testing is the only way in which meaningful results, as to the actual wounding effect of bullets, can be obtained. Firing into human cadavers and live animals are both, however, extremely sensitive subjects and are open to much adverse comment.

In an attempt to set some standard by which a bullet' s performance may be measured without shooting cadavers or live animals, many different materials have been used to simulate body tissue. Among these are wet telephone books, bars of industrial soap, Plasticine, Dukseal, water and 'ballistic gelatine'. Whilst most of these can be used for strictly comparative purposes, they do not give a realistic picture as to how the missile will perform in human tissue.

The only medium which gives a close approximation as to the effects of a bullet on human tissue is ballistic gelatine.

Water also gives an approximation as to the expansion capabilities of various bullet constructions, but it does not, of course, give any indication as to the temporary and permanent cavity produced.

Ballistic gelatine (from Gelatin Manufacturers Institute of America Inc., www. gelatin-gmia.com) is made by dissolving type 250 A ordnance gelatine in water to make a 10% solution. During the preparation, the temperature of the gelatine solution should never be allowed to rise above 40 °C as higher temperatures result in hardening of the gelatine. The solution should be set in a refrigerator at 4 °C for at least 36 h and the blocks should be used within 30 min of removal.

After use, the blocks may be reconstituted by re-melting at a temperature not exceeding 40 °C and set in a refrigerator as before.

Theoretically, the wounding effect of a bullet would depend upon its striking energy, that is, kinetic energy. But here, theory and practice decidedly part company. Other factors have a very profound effect on the bullet' s effect in animal tissue or other simulant, including the bullet shape, cross-sectional density, weight, speed and bullet construction.

Major Julian Hatcher was one of the first to seriously attempt to assign a numerical figure to the wounding capabilities of a particular bullet/cartridge combination (Hatcher, 1935). He called the numerical value the 'relative stopping power' (RSP).

The original formula he used to calculate the RSP was as follows:

RSP = bullet cross sectional area x muzzle energy x shape factor

Hatcher came to realize, however, that this formula was flawed, as the factor which permits the transfer of velocity to the surrounding tissue is not the muzzle energy of the bullet but rather its momentum.

He therefore modified his formula for RSP using momentum as follows: RSP = bullet cross sectional area x momentum x shape factor.

The shape factor was an empirical figure assigned by Hatcher. The factors he gave for various bullets are as follows:

• round-nosed jacketed bullet = 900;

Table 3.14 Relative stopping power (RSP) of various bullets.

Cross-sectional

Cartridge

Momentum

area

Shape factor

RSP

0.22" Long rifle

0.097

0.039

1000

3.8

0.25" ACP

0.083

0.049

900

3.7

7.65 mm Parabellum

0.246

0.075

900

16.6

0.32" ACP

0.147

0.076

900

10.0

0.38" Super Auto

0.347

0.102

900

31.8

9 mm Parabellum

0.288

0.102

1000

29.4

0.38" Special

0.302

0.102

1000

30.8

0.44" Special

0.416

0.146

1000

60.6

0.45" ACP

0.420

0.159

900

60.0

Using Hatcher's figures, we can construct Table 3.14.

The momentum is measured in pounds feet per second and the cross-sectional area in square inches.

A major contribution of this formula was the recognition that the bullet' s cross-sectional area has a very significant effect on its effectiveness in animal tissue. This gave a useful set of figures for direct comparison purposes between various bullet configurations, but it was not in total agreement with actual case incidents.

In 1973, the American National Institute of Law Enforcement and Criminal Justice sponsored research into determining the effectiveness of handgun cartridges as definitively as technology, at that time, would permit.

The effectiveness of a bullet configuration was given a numerical value called the Relative Incapacitation Index (RII). This was calculated on the basis of three factors, target vulnerability, hit distribution and bullet terminal ballistics.

Target vulnerability was calculated by determining the relative sensitivity of the various areas of the body. This was done by dividing an anatomical model of the human body into 1 in. thick slices. Each of these horizontal slices was then divided into rectangular solids by vertically imposing a 0.2" square grid onto the slice. Doctors then assigned a numerical value to each of these rectangular solids representing the vulnerability of that solid. This formed the basis of the 'computer man' which was used as a vulnerability model for the study.

Hit distribution was obtained by live firing using soldiers firing 0.45" Colt self-loading pistols at ' pop-up' targets. The hit distribution data was weighted against the penetration data in the anatomical model with respect to incapacita-tion potential.

The bullet terminal ballistics data was obtained by an examination of the bullet's behaviour in 20% gelatine (this is counter to the normal use of 10% gelatine), a standard set by the US Army Surgeon General. The factor used in determining the potential wounding capability of the bullet was to measure, via high-speed motion picture, the temporary cavity formed in the gelatine.

Table 3.15 Relative Incapacitation Index (RII).

Calibre

Weight (grains)

Bullet type

Velocity (ft/s)

RII

0.44" Mag

200

JHP

1277

54.9

0.38" Spl+P+

125

JHP

1108

25.5

0.45" ACP

185

JHP

895

21.1

0.357" Mag

158

JSP

1030

17.5

0.357" Mag

158

WC

821

14.7

0.357" Mag

158

JHP

982

11.1

9 mm PB

125

JSP

1058

9.9

0.38" Spl

125

JHP

911

7.0

0.45" ACP

230

FJ

740

6.5

0.38" Spl

158

LRN

795

5.0

0.22" LR

37

LHP

872

2.3

JSP, jacketed soft point; FJ, full jacket; JHP, jacketed hollow point; WC, wadcutter; LRN, lead round nose; LHP, lead hollow point; +P+, a very high-pressure cartridge available only to police departments.

JSP, jacketed soft point; FJ, full jacket; JHP, jacketed hollow point; WC, wadcutter; LRN, lead round nose; LHP, lead hollow point; +P+, a very high-pressure cartridge available only to police departments.

It is interesting that a dramatic 'ballooning' effect was noted in the temporary cavity when the projectiles' velocity exceeded 1100 ft/s, which is approximately the speed of sound in air.

In calculating the RII figures, the analysis was run using the centre of vulnerability of the computer man which is located in the chest area at armpit level. These results give the RII figures seen in Table 3.15.

This is a very abbreviated table as there were 142 different cartridges evaluated in the original paper. It does, however, give some interesting data. For example, the 0.45" ACP, which has always been considered to be a very effective round, is rated only marginally better than the 0.38" Spl lead round nose (LRN) which has long been recognized as totally inadequate in a combat situation.

Using these figures, it was considered that any round with an RII below a factor of 9.0 was not suitable for a military or police round.

In 1991, a privately funded group was formed to study the physiological effects of bullet impact on medium-sized animals. These are now known as the Strasbourg tests. These tests were politically very sensitive in nature as the animals were shot whilst in a conscious condition.

The animals selected were French Alpine goats as they were very similar in weight, lung capacity and thoracic cage dimensions to those of man. To measure the effects of being shot, transducers were implanted in the carotid artery and electroencephalograph needles inserted into the scalp.

The animals were shot in the lung area as this was considered the most likely place a human being would be struck by a bullet. In all, there were a total of 611 goats shot during these tests.

The results for these tests are in the form of ' average incapacitation time ' (AIT), which is deemed to be the average time (usually over tests on five indi vidual goats) it took the animal to collapse and be unable to rise again. A selection of the results follow (Table 3.16). When reviewing these results it should be noted that there is some speculation as to whether these tests ever took place with such comments as ' Strasbourg was either done in the Goat Lab at Bragg [US Military Base in Texas, USA], or a replication of that lab, or someone who is familiar with that lab did a helluva thorough job constructing an elaborate hoax.' (Retired US Army Special Forces officer) being common.

Evan Marshall, an ex-patrol officer with the Detroit Police Force, spent 15 years collecting data on actual shooting incidents. Any incident where one shot was sufficient to incapacitate the assailant so that he was incapable of further fight was classified as a one-shot stop. Some of his figures are given in Table 3.17.

Table 3.16 A selection of results from the Strasbourg Tests showing the average incapacitation time (AIT) for various rounds.

Calibre

Weight (gr)

Bullet type

Velocity (ft/s)

AIT

9 mm PB

115

JHP

1175

9.3

9 mm PB

115

FJ

1163

14.4

9 mm PB

147

JHP

962

9.68

0.45" ACP

185

JHP

939

10.66

0.45" ACP

230

FJ

839

13.84

0.45" ACP+P

185

JHP

1124

7.98

0.38" Spl

158

RNL

708

33.68

0.38" Spl

125

JHP

986

14.28

0.38" Spl+P

125

JHP

998

10.92

0.38" Spl+P

158

LHP

924

10.86

Table 3.17 Abbreviated list of Marshall's 'one-shot stops'.

Weight

Bullet

Velocity

Total

One-shot

Calibre

(gr)

type

(ft/s)

shootings

stops

Percentage

0.38" Spl

158

RNL

704

306

160

52.28

0.38" Spl+P

158

LHP

926

114

79

69.29

0.38" Spl+P

158

JHP

991

183

126

68.85

0.38" Sp1+P

110

JHP

1126

16

11

68.75

9 mm PB

115

FMJ

1149

159

99

62.26

9 mm PB

115

JHP

1126

32

20

62.50

9 mm PB

147

JHP

985

25

19

76.00

9 min PB+P+

115

JHP

1304

76

68

89.47

0.357" Magnum

158

JHP

1233

23

22

81.48

0.357" Magnum

125

JHP

1391

83

73

87.95

0.357" Magnum

125

JHP

1453

426

448

96.96

LHP, lead hollow point; JHP, jacketed hollow point; RNL, round nosed lead.

LHP, lead hollow point; JHP, jacketed hollow point; RNL, round nosed lead.

Of all the various tests and simulations dealing with handgun ammunition effectiveness, probably the most important is the Marshall list of 'one-shot stops'.

From all the above, it is clear, however, that even La Garde in 1904 had it correct in that it is not the velocity which really matters; it is the necessity of getting a large-calibre missile deep into the body. Back in 1904, this was done with large, 0.455" and 0.476", calibre, slow-moving missiles which punched their way through the tissue. Today, the move is towards smaller missiles but with a hollow point which, when travelling in excess of 900 ft/s, will expand to give the effect of a large-calibre missile.

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