Pistol cartridges including .22LR, .32ACP, .380ACP, 9x19mm, .40S&W, .45ACP, .357 Magnum, .44 Magnum JHPs as well as 22 K-Hornet, 223 Remington, 260 Remington, 308 Winchester and 30-06 Springfield rifles were evaluated in 20-percent ballistic gelatin and the results recorded on high speed video. From these videos, analysis was conducted of the velocity and instantaneous kinetic energy of the point of maximum temporary cavity diameter for each shot.

As a projectile penetrates a fluid medium, a cavity is created rearward of the projectile as a consequence of the previously static fluid body being forced around the edges of the penetrating object. Here we will present the velocity of this radial expansion inside of the ballistic gelatin block, for a wide variety of practical handgun and rifle calibers. Debate has existed since at least 1904¹ as to the wounding effects, if any, of this temporary cavity and whether or not it forms at all inside of a human body. Informed opinion varies from ‘no wounding effect at all’ to ‘both handgun and rifle velocity cartridges wound the periphery of the track’. Early research programs designed to establish a base of comparison between cartridges such as the Relative Incapacitation Index did place a heavy emphasis on the wounding effects of temporary cavitation from handgun ammunition².

In view of quantifying any potential wounding effects of the temporary cavity expansion, the kinetic energy of the cavity was measured by assuming the analyzed segment of the track to be a disc with a uniform diameter corresponding to the measured temporary cavity diameter at a given time and a thickness of 0.10” inch. Using the density of 20-percent ballistic gelatin, a weight for the given compressed section was determined and thus, the kinetic energy was calculated from the mass of this section and the instantaneous measured velocity. Being constrained on this report to work within the (very limited) publicly-available data set for human survivability, we set the upper limit of non-injury to be that of the kinetic energy corresponding to a commercial BB gun at 430 ft/sec. Hits with this weapon are not generally associated with fatal wounds, so should provide a somewhat realistic representation of what could be expected to happen to unprotected internal organs being stressed by an equivalent force.)

With a peak radial kinetic energy of 0.44 ft-lbf, the .22LR JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 0.49 ft-lbf, the .32ACP JHP is not capable of creating damage outside of the tissue that it directly crushes.

Absent tumbling, with a peak radial kinetic energy of 0.035 ft-lbf, the .380ACP 95gr FMJ is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 0.72 ft-lbf, the .380ACP 90gr Federal Hydra-Shok JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 0.72 ft-lbf, the .380ACP 102gr Remington Golden Saber JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 1.25 ft-lbf, the .380ACP 90gr Speer Gold Dot JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 1.96 ft-lbf, the 9x19mm 124gr Remington +P Golden Saber JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 0.55 ft-lbf, the 9x19mm 147gr Remington Golden Saber JHP is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 7.85 ft-lbf, the radial movement of tissue away from a 357 Magnum 125gr Speer Gold Dot JHP (at 1405 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 850 ft/sec. At that velocity, a steel BB is capable of penetrating well over 4” of 10-percent ballistic gelatin.

With a peak radial kinetic energy of 2.29 ft-lbf, the radial movement of tissue away from a 40S&W 180gr Speer Gold Dot Short Barrel (at 970 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 459 ft/sec. This is a kinetic energy sufficiently high to disable an organ with ballistic resistance similar to a human eye.

With a peak radial kinetic energy of 2.26 ft-lbf, the radial movement of tissue away from a 45ACP 185gr Remington +P Golden Saber (at 1024 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 456 ft/sec. This is a kinetic energy sufficiently high to disable an organ with ballistic resistance similar to a human eye.

With a peak radial kinetic energy of 1.28 ft-lbf, the 45ACP 230gr Remington Golden Saber JHP (impacting at 817 ft/sec) is not capable of creating damage outside of the tissue that it directly crushes.

With a peak radial kinetic energy of 1.47 ft-lbf, the 45ACP 230gr Federal Hydra-Shok JHP (impacting at 833 ft/sec) is not capable of creating damage outside of the tissue that it directly crushes.

Unsurprisingly, the .44 Magnum 240gr Speer Gold Dot JHP, with a peak radial kinetic energy of 9.6 ft-lbf, is more than capable of injuring structures immediately adjacent to the penetration track. For reference, an initial kinetic energy of 9.6 ft-lbf is sufficient to propel a 0.177” steel BB at 939 ft/sec.

We begin to see the value in the adage “velocity kills”. The maximum temporary cavity kinetic energy now is equivalent to a 0.177” steel BB at 1109 ft/sec.

With a peak radial kinetic energy of 21.8 ft-lbf, the radial movement of tissue away from a 223 Remington 55gr Barnes TSX (at 2976 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 1416 ft/sec.

With a peak radial kinetic energy of 20.1 ft-lbf, the radial movement of tissue away from a 260 Remington 120gr Nosler Ballistic Tip (at 2575 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 1359 ft/sec.

With a peak radial kinetic energy of 17.5 ft-lbf, the radial movement of tissue away from a 308 Winchester 150gr Federal Fusion JSP (at 2691 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 1268 ft/sec.

With a peak radial kinetic energy of 87.4 ft-lbf, the radial movement of tissue away from a 30-06 Springfield 55gr Remington Accelerator JSP (at 3857 ft/sec impact velocity) is capable of creating a wound similar to a 0.177” steel BB traveling at 2835 ft/sec.

In terms of projectile wounding through temporary cavity expansion, there is no replacement for velocity. Expanded diameter appears to play little, if any role in this phenomenon. Conventional JHP ammunition in 9x19mm, .40S&W and .45ACP are on the borderline of being able to provide an increase in lethality from temporary cavity expansion. Cartridges for concealed handguns such as .380ACP and smaller, appear to be only able to wound the tissue that is directly in contact with the bullet. Rifle cartridges are almost a class apart from handgun cartridges in this regard, and given the reported effectiveness of rifles in combat, it is possible that this wounding mechanism is quite applicable to many shotlines through the body.

While not a primary wounding mechanism, the secondary effect of wounding through tissue expansion is worthy of further study as both an aid to future ammunition design and firearm forensic investigations.

¹ Thompson-Lagarde Report; MAJ Louis A. La Garde and CPT Jno. T. Thompson. Philadelphia, PA: 1904.

² Ammunition for Law Enforcement: Part I Methodology for Evaluating Relative Stopping Power and Results; William J. Bruchey Jr. Technical Report ARBRL-TR-02199. Aberdeen Proving Ground, MD: 1979.