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It is concluded from a comprehensive ballistic and metallurgical evaluation of three samples of 3/8 in. rolled homogeneous armor that: (a) In the penetration-through-plate tests of Spec. AXS-488-3 involving the use of cals. . 30 and .50 AP M2 projectiles, the maximum acceptable exit diameters are too large, allowing the acceptance of armor of inferior ballistic characteristics. (b) Jacket-less caliber .50 AP projectiles can be developed for use in the projectile-through-plate test. (c) The 20 MM H.E.I shock test of Spec. AXS-488-3 is an integrative test possessing attributes both of shock and steel soundness tests. Although the 20 MM H.E.I. test does yield valuable information relative to the ballistic characteristics of armor, the development of a more suitable shock test is recommended.

Range, wind tunnel, and instrumented free-flight tests have shown that a subcaliber boom at the base of a spin-stabilized projectile will produce significant changes at both small and large yaws. Almost all properties, but in particular the static and magnus moments, are affected. These aerodynamic changes, together with the inertial properties of the shell, are shown to affect both the static and the dynamic stability adversely.

The method of calculating the behavior of a projectile propelled by a pre-burned propellant in a chambered gun is reviewed. The influence of gas in front of the projectile in the barrel is discussed, as is the procedure to take account of gas frictional and heat-transfer effects. The method of calculation by hand of the perform-ANCE OF TWO-STAGE GUNS IS THEN OUTLINED. Some results obtained from an electronic computing machine are compared with experimental results.

To determine the response of human cortical bone to projectile impact, 364 projectile impact tests were conducted on the shafts of embalmed human femurs. Chrome steel spherical projectiles in two diameters, 0·250 and 0·406 in., were employed to differentiate the effects of projectiles of varied sizes and masses in impacts at the same velocity. It was found that the larger projectiles expended significantly more energy in fracturing a femur than the smaller projectiles did at an identical impact velocity. Also, when impacts in which larger and smaller spheres possessed identical kinetic energies were compared, it was found that the larger spheres still expended more energy in fracturing the femur. Finally, it was clearly demonstrated by these experiments that impacts to cortical bone of the femoral shaft by either size projectile caused greater energy expenditure than impacts to the distal end of the femur, which is composed almost entirely of cancellous bone.

The results of an exterior ballistics test of the M193 ball projectile when launched from the M16A1 rifle are presented and discussed. Rifles with twists of 1 turn in 12 inches and 1 turn in 14 inches were used in the tests. Data were gathered from test firings at the small Aerodynamics Range and the Transonic Range of the Ballistic Research Laboratories and from a temporary range set up in the Climatic Hangar at the Eglin Air Force Base, Florida. Tests at Eglin were conducted at air temperatures ranging from +125 deg. F to -65 deg. F. (Author)

Chemical analysis of the lead cores and hardness and thickness measurements of the jacket components and lead cores of five caliber .45 M1911 pistol ball projectiles indicate that four of the projectiles are similar. The lead core of one projectile is more highly alloyed and consequently hardner than the others. Slightly lower ballistic limits against helmet and body armor steel are expected from bullets similar to the harder one.

Background Modern high-velocity projectiles produce temporary cavities and can thus cause extensive tissue destruction along the bullet path. It is still unclear whether gelatin blocks, which are used as a well-accepted tissue simulant, allow the effects of projectiles to be adequately investigated and how these effects are influenced by caliber size. Method Barium titanate particles were distributed throughout a test chamber for an assessment of wound contamination. We fired .22-caliber Magnum bullets first into gelatin blocks and then into porcine hind limbs placed behind the chamber. Two other types of bullets (.222-caliber bullets and 6.5 × 57 mm cartridges) were then shot into porcine hind limbs. Permanent and temporary wound cavities as well as the spatial distribution of barium titanate particles in relation to the bullet path were evaluated radiologically. Results A comparison of the gelatin blocks and hind limbs showed significant differences (p < 0.05) in the mean results for all parameters. There were significant differences between the bullets of different calibers in the depth to which barium titanate particles penetrated the porcine hind limbs. Almost no particles, however, were found at a penetration depth of 10 cm or more. By contrast, gas cavities were detected along the entire bullet path. Conclusion Gelatin is only of limited value for evaluating the path of high-velocity projectiles and the contamination of wounds by exogenous particles. There is a direct relationship between the presence of gas cavities in the tissue along the bullet path and caliber size. These cavities, however, are only mildly contaminated by exogenous particles.

It was determined that tempered glass automobile windows may severely influence the trajectory of .38 Special projectiles. In replicating an actual case situation, deflections as great as 26.4 degrees were observed with jacketed hollow-point ammunition, and as high as 10.8 degrees for lead ammunition.

Small angles of projectile entry are difficult to determine in two-dimensional targets or in three-dimensional targets where internal deflection has taken place. This results from the fact that small errors in measurement lead to large errors in the calculation of the sine function used in the estimation of the angular projection of a circle onto an inclined plane at angles of less than 20° from the normal. The use of a bullet tip scale, constructed to the dimensions of the entering projectile, allows a significantly more accurate determination of small angles of entry in targets not subject to stretching. A comparison of the relative error inherent in calculating entry angle using the sine function and measuring the angle using the bullet tip scale demonstrates the suitability of using the tip scale at angles less than 20° and the sine function at entry angles greater than 20°.

Great controversy has surrounded the replacement of the 7.62-mm caliber by the reduced 5.56-mm caliber as the standard U.S. military rifle. Although its relevance to human wounding can be debated, the terminal ballistics of military small arms in ordnance gelatin remains a convenient medium for comparative testing. In the present study, 7- by 10- by 24-in. (18 by 25 by 61 cm) blocks of 20% ordnance gelatin were fired upon from a range of 19 ft (6 m) under high-speed cinemagraphic surveillance. The tendency of the M193 5.56-mm full metal jacket projectile to break up in soft tissue simulant was confirmed as a fundamental difference from the 7.62-mm M80 NATO ball.

SPARK photography, in which the illumination is provided by an electric spark of such short duration that a moving object appears stationary, has many applications in the investigation of high-speed phenomena. The record obtained is not an image, no lens being used, but is simply the silhouette of objects between the light source and the photographic plate. Two distinct problems are presented in the photography of moving objects. One of these is the timing of the spark so that the desired epoch of the phenomenon under investigation may be photographed, and the other has to do with the duration of the spark. All the photographs described in this article were taken on plates not larger than 8 by 10 inches. A projectile moving at a speed of 2700 feet per second would be in front of such a plate, and therefore in a position to be photographed, for only 0.0003 second. If the projectile is to be photographed within an inch of a predetermined position, the time of occurrence of the spark must be correlated with the position of the projectile to within 0.00006 second.

MESSRS. Payman and Woodhead appear to have misunderstood the method described in our letter in NATURE of Dec. 27, p. 994. We made no claim to originality of application of the principle of light interception. Our method does not depend on shadow or ordinary photography, which has been used in ballistics since the time when Boys took his first shadow photographs in 1893, and differs from that used in other optical chronographs (see, for example, Cranz, “Experimented Ballistik”, 3, chap, ii., 1927), of which Kampe de Feriet's is one.