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The Military Effectiveness of Pistol Cartridges: An analysis of the .45 acp versus the 9x19mm in military service
by Charles Q. Cutshaw

In 1898, at the end of the Spanish-American War, Spain ceded the Philippines to the United States, who quickly moved in to take over. Filipino insurgents, dissatisfied at the prospect of United States military rule, mounted an armed insurrection that lasted from 1899 until 1902, while beginning a small arms controversy that continues to this day. The US Army was sent in to pacify the rebels, and the soldiers were issued the Model 1892 Colt double action .38 caliber revolver. They found, much to their dismay and more often than not to the detriment of their continued good health, that the .38 caliber bullets fired by their new revolvers were incapable of quickly incapacitating the machete-wielding Moros. The Moros would attack American forces from the jungle after having first whipped up their levels of ferocity and fanaticism with liberal doses of mind-altering drugs.

The Colt Model 1892 double-action revolver in .38 Long Colt cartridge was adopted by the War Department in 1892. The theory was that the higher velocity of the .38 would make up for the bullet’s lighter weight and smaller diameter. The problem that was so existentially manifested in the Philippine Insurrection was that the .38, apparently unlike the .45 Colt that preceded it, lacked sufficient “stopping power” to reliably disable a man who was shot with it, especially if that man happened to have infused himself with drugs that made him virtually immune to pain. In the wake of the failure of its new handgun, the Army was forced to withdraw many “obsolete” M1873 single-action .45 Colt revolvers from storage for use in the Philippines. The Army also ordered just over 5,000 M1903 Colt .45 double-action revolvers for use in the Far East. However, the war was over before they saw any significant action and before the actual effectiveness of the .45’s could really be determined. Most of the M1903 revolvers were subsequently issued to the Philippine Constabulary.

The demonstrated inadequacy of the .38 cartridge caused the War Department to re-evaluate its thinking regarding the caliber of the military’s handgun cartridge. In April 1903, Secretary of War Elihu Root established a board to study the problem and decide what cartridge would have the most, “... stopping power and shock effect at short range necessary for a pistol for the military service.” Among the cartridges tested was the 9x19mm Parabellum, which had been introduced into German military service in 1902 to replace the 7.65x21mm (.30 Luger) pistol cartridge. The .45 Automatic Colt Pistol (ACP) cartridge, today often thought of as antiquated in comparison to the “high-tech” 9x19mm, was not introduced until 1909 and thus was not tested. Secretary Root’s board of officers set out to conduct definitive tests of pistol stopping power using some pretty grisly methods; in fact, part of their tests would surely have resulted in vehement protests by animal rights groups had they been undertaken today.

The first tests involved shooting human cadavers suspended by their necks so their feet cleared the floor. The idea was to determine the nature of wounds inflicted by various caliber bullets on bones and soft parts of the body, along with the shock effect of each bullet fired. This was measured by determining the amount of movement of limbs from the moment of impact, with greater movement earning a higher score for a maximum of 100. Wounds were examined using both X-ray and dissection. After eleven tests, the board found that the shock effect of a given bullet was in proportion to its sectional area, i.e., the greater the diameter of the bullet, the greater shock effect.

The board next moved to the Chicago stockyards to conduct tests on some live horses and cattle about to be slaughtered. The intent of this series of tests was to learn the immediate result of shock effect and stopping power of each bullet when striking various parts of the animals’ bodies. Slow fire tests were conducted by shooting the hapless cattle in the chest and abdomen at timed intervals. At the end of this test, a quick-firing shoot was conducted in which the animal was rapidly shot until it fell to the floor. If the animal did not fall within a few shots, it was dispatched instantly by stockyard employees. There were a total of thirteen of these tests on living cattle that again led to the conclusion that bullet sectional area was more important than velocity in general shock effect and destruction of tissue. The final tests were conducted on living and dead horses that led the board to conclude that the effect of revolver bullets on the bones of horses was identical with that of humans. In the end, the board rated the 9x19mm the same as the obsolescent .45 Colt in human cadavers, but the .45 was decidedly superior against living animals. The .45 Colt typically dropped the animal it was used against within six shots, while an animal shot in the identical places with the 9x19mm was still standing after twelve shots and had to be dispatched by slaughterhouse employees.

The 9x19mm Parabellum ballistics are similar to today’s standard US M882 9mm. The .45 round that was used in the tests was the venerable .45 Colt, introduced by the U.S. Army in 1873. With a muzzle velocity of 720 fps and muzzle energy of only 288 foot pounds, the old .45 should not have performed nearly as well as the 9x19mm round during the 1903 tests. This round fired a 124-grain bullet at over 1,000 fps, resulting in a muzzle energy of 301 foot pounds. As noted, the 9x19mm nonetheless did not fare well against the .45 Colt in the 1903 tests, nor did its smaller predecessor, the 7.65x21mm (.30) Luger. In theory, the 7.65x21mm cartridge should have performed even better than the 9x19mm because it had a muzzle velocity of over 400 fps greater and over 100 foot pounds more muzzle energy than its larger relative. Despite this, the 1903/1904 tests seemed to prove beyond doubt that a large, relatively slow moving bullet was more effective than a small, extremely fast one.

The summary of the Army tests published in March 1904 went into great detail regarding wound ballistics and compared the results of various types and calibers of bullets. It particularly noted the explosive effect of high-velocity rifle bullets on living tissue and compared the effects of small, high-velocity pistol bullets versus those of large slower moving ones. The report concluded that the effectiveness of bullets increases in direct proportion to mass, rather than velocity. In other words, if a small, fast bullet is effective, a large, heavier one at the same or even somewhat less velocity than the smaller one is even better.

While the turn of the century tests were not particularly scientific by modern standards, their results have been repeatedly confirmed throughout the intervening years. We should note, however, that the tests were probably more objective than modern ones because of the lack of government/political interference. Further, the 1903 test results have been subsequently duplicated and validated, based on independent unbiased empirical testing. For example, Col Julian Hatcher conducted effectiveness testing of pistol cartridges for his 1935 Textbook of Pistols and Revolvers in which the relative stopping power of the .45 ACP was rated some 60% greater than the 9x19mm. Hatcher’s conclusions are fully in line with those of Col. Lagarde in 1903 and he concludes in part, “All the tests of which the author has any knowledge..., indicate that caliber is by far the most important factor in stopping power.” The .45 ACP has consistently proven to be more effective in incapacitation ability than the 9x19mm Parabellum, although the reasons why this is so may not be readily apparent in testing.

Beginning in 1990, the Federal Bureau of Investigation conducted tests to rank the relative effectiveness of a variety of pistol cartridges. These tests evaluate the ability of various handgun bullets to meet FBI performance standards via the fairly complex FBI Ammunition Protocol. The goal of the FBI tests is to determine a specific cartridge’s ability, “... to inflict effective wounds after defeating various intervening obstacles commonly present in law enforcement shootings.” (Emphasis in original) The 230-grain full metal jacket round rated 100% penetration success rate in the FBI tests, while the best 9x19mm round, the 124-grain NATO, achieved 95.5% in the FBI Penetration Protocol. This difference is small, but it must be remembered that the US M882 has less energy than the standard NATO round and penetration is only one aspect of ammunition effectiveness. Indeed, lethality was never an issue in development of the US M882 9x19mm round. On the contrary, it would appear that the M882 was developed because the M9 pistol had rail and locking block failures when firing ammunition that is more potent.

Full metal jacket (FMJ) bullets used by the military are inherently poor antipersonnel munitions because they do not expand upon entering a human body. Bullets that expand (dum-dum bullets) are outlawed for military use by The Hague Convention of 1899 and the Geneva Convention of 1905. Lack of expansion reduces the inherent shock of the bullet by reducing the temporary cavity and contributing to over penetration. Bullets that penetrate too deeply are claimed by some to be almost undesirable for police or self-defense use as those which lack sufficient penetration because they may pass through a human body without hitting or damaging any critical organs and hit an innocent by-stander. Ideally, a bullet, whether or not it is of the expanding type, should penetrate at least 12 inches into ballistic gelatin to be considered an effective antipersonnel round. Recent research suggests that if the military really wishes to have a pistol cartridge of maximum effectiveness for personal defense, then the 9x19mm round is inappropriate. In order to understand why this is so, it is necessary to understand bullet wounding mechanisms.

In the movies, “bad guys” (and good guys, as well) are typically shot and almost immediately fall down either dead or totally incapacitated. In the real world, people who are shot are rarely rendered instantly incapable of any further physical action. Even when shot in the heart, a usually fatal wound, a person will still have 10 to 15 seconds of consciousness remaining before blood loss to the brain causes unconsciousness. This is a virtual lifetime in combat, when a single second may make the difference between life and death. The only situation in which incapacitation is instantaneous is a central nervous system hit, either in the brain or brain stem. Otherwise, it is likely that the person shot will be capable of some level of physical activity. Just how much physical activity a fatally wounded person would be capable of varies greatly and is dependent upon so many variables that it is beyond the scope of this brief paper. Suffice to say that single shot immediate incapacitation by pistol bullets is the exception and not the rule. That fact is the reason for the “double tap” used by many special operations and police forces. Even so, there are many documented instances of individuals being shot several times both with 9x19mm and .45 ACP bullets without significant incapacitation.

The reason why an individual can be shot several times without incapacitation is a complicated subject. Books have been written on the topic over the years and even with modern testing, the debate over bullet effectiveness has yet to be laid to rest. There are, however, three fundamental mechanisms of injury: laceration/crushing, stress waves and temporary cavitation. Laceration is the primary injury method used by subsonic projectiles and can often be compared to a very deep stab wound. Unless major organs, blood vessels, or bones are struck, the laceration and crushing effect of a nonexpanding bullet is generally not serious.

Stress waves are caused by high velocity bullets forcing their way through tissue, which is some 300% denser than air. As the bullet moves through tissue, it compresses it and forms a spherical shock wave that moves away from the bullet at approximately 1,500m/s. This shock wave lasts only about a millisecond, but reaches a peak overpressure of approximately 100 atmospheres. Tissue inertia precludes any actual movement or transfer, but nerve damage may occur at some distance from the permanent wound cavity. This phenomenon is associated almost exclusively with high-velocity rifle bullets, although a hit by a pistol bullet near the solar plexus or their nerve center might be sufficient to cause incapacitation in that it is similar to a hard punch in that area. This might explain why pre-fragmented low penetration bullets such as those manufactured by Glaser and MagSafe have been claimed to be so effective for quick incapacitation. This is, however, speculation; as there have been no tests known to this writer that attempt to measure the neural shock caused by stress waves induced by a bullet striking near a major nerve center such as the solar plexus. A sharp blow to that area will, however, quickly incapacitate most individuals although there is little or no issue damage.

Temporary cavitation resulting from the impact of a high velocity bullet, however, can cause severe injury. It is rare for a pistol bullet to achieve velocities sufficient to cause severe temporary cavitation; as with stress waves, this phenomenon most often results from the strike of a high velocity rifle bullet. As a bullet enters the body, momentum is transferred to the surrounding tissues, causing them to move and oscillate even after the projectile has passed. This creates a large cavity that may reach over 30 times the diameter of the bullet in extreme cases. The cavity goes through several pulsations in only a few milliseconds before returning to a permanent shape only slightly larger than the permanent wound cavity. The violent oscillations caused by the passage of the bullet are sufficient to damage organs, blood vessels and nerves outside the immediate path of the projectile. Except for one or two magnum cartridges, pistol bullets do not have sufficient velocity or mass to cause the violent temporary cavitation necessary for tissue destruction.

The temporary wound cavity is usually associated with high-powered rifle bullets or certain high-velocity pistol magnum rounds, such as the .357 or .44 magnum. Even these two rounds, however, cause far smaller temporary wound cavities than rifle bullets. With all other pistol bullets, the temporary wound cavity may be as much as ten times the diameter of the permanent wound cavity, but this “...does not exceed the elastic limits of the tissue, and little damage is done outside the bullet path.” In other words, the temporary cavity caused by most pistol bullets does not tear the tissue, as it would if the bullet were from a high-powered rifle - it merely stretches it, whereupon the tissue returns to its approximate original position, less the tissue displaced by the bullet’s passage. The FMJ bullet used for military handguns is the least effective type of pistol ammunition for antipersonnel purposes.

As previously noted, the permanent wound cavity is almost like a knife wound unless the bullet strikes a major organ, blood vessel, or a bone. Otherwise, it will have little serious effect or “stopping power.” This is because full metal jacketed pistol bullets have relatively little energy available to cause damage, despite claims that either the 9x19mm or .45 ACP is a more effective military round. It is a misconception that any person hit with a .45 bullet will be knocked down. Essentially, the only way to improve the wounding effectiveness of a full metal jacketed pistol bullet is to design it so that it becomes unstable upon striking a target, thus causing it to “turn” thereby enlarging the permanent wound cavity. An unstable bullet, however, will have less penetrating ability against “hard” targets such as thin steel and protective clothing. It must be emphasized that with any handgun, the permanent wound cavity is the absolute deciding factor for rapid incapacitation. Both the 9x19mm and .45 ACP pistol bullets as used by the military are stable and will pass through tissue with little damage outside the permanent wound cavity. Consequently, both rounds in their military configuration are considered by small arms experts to be poor choices for self-defense. This fact has emerged in Afghanistan, where the M9 9mm pistol has been essentially used in combat for the first time since its adoption. There have been several admittedly anecdotal reports from special forces troops using 9mm handguns having to shoot enemy soldiers several times to incapacitate them. These soldiers concluded their reports by asking for .45 caliber pistols to replace their 9mm ones. It is not known whether or not the pistols were replaced.

Many apologists of the 9x19mm point to the improved range scores since the M9 pistol was adopted by the military. The fact is that the .45 ACP M1911A1 pistols on hand in virtually all military arms rooms in the 1970’s and 1980’s were simply worn out, the most recent military production having been in 1945. Most M1911A1 pistols selected from military arms racks would actually rattle when shaken, a sure sign that the internal components no longer fit together as they were designed. (This writer observed this condition as long ago as the 1960s while serving as a US Army infantry officer.) A worn out gun will not shoot accurately. Newly manufactured high-quality Government Model 1911A1 style pistols are inherently as accurate as the M9; the accuracy problem was worn out pistols, not ammunition.

Another fact often espoused by 9mm apologists is that the United States had agreed with NATO that when it got around to replacing the M1911A1, the caliber would be 9x19mm to ensure commonality, or that Congress mandated the decision. This argument is likewise irrelevant; if the United States had decided to continue with the .45 ACP, it would not be the first time that the US rammed an ammunition decision down NATO’s throat, as was the case with the 7.62x51mm and 5.56x45mm rifle cartridges.

The final argument for the 9mm is “firepower.” Most recent 9x19mm pistols have a magazine capacity of 12 to 18 rounds of ammunition. At one time, this was a partially relevant argument, although the case can be made that with proper bullet placement, a dozen rounds of ammunition are not necessary. Even so, today’s .45 ACP pistols are very close to the “wonder nines” in magazine capacity. The Para Ordnance P14 modification of the venerable Colt Government Model .45 holds 13 rounds in its magazine, as does the Glock 21, a “state-of-the-art” automatic pistol. Further, the Heckler and Koch Mark23 SOCOM offensive handgun has similar magazine capacity, as does the company’s USP45 Tactical. The 9x19mm “firepower” argument thus has little merit.

It is germane to our analysis to examine the most recent handgun requirement for the US military, viz. the United States Special Operations Command (USSOCOM) Joint Services Operational Requirement (JSOR) for an offensive handgun that resulted in adoption of the Heckler & Koch Mark23. The JSOR mandated that the offensive handgun would be .45 ACP caliber. The JSOR stressed the following operational/close combat issues:
  • Incapacitation of the enemy in the shortest period of time.
  • The inability of the shooter to ensure a central nervous system hit due to the fluid nature of the close quarters battle.
  • High probability of a random torso shot.
  • Maximum wound cavity when using subsonic ammunition.

While not all military special operations units use the Mark23, many continue to employ .45 ACP pistols in the form of modified “tuned” M1911A1 pistols, such as the Marine Corps’ MEU-SOC 45. (Marine Corps Expeditionary Unit - Special Operations Capable.) The fact that all FBI special units, such as the Hostage Rescue Team and SWAT Teams now employ .45 ACP pistols exclusively is also informative.

The cross sectional area of the .45 ACP 230-grain bullet is .160 square inches; the cross sectional area of the 124-grain 9mm NATO bullet is .0989 square inches. The 9mm possesses only about 62% of the cross sectional area of the .45 ACP. A more traditional method of establishing the effectiveness of a given bullet is its sectional density, the ratio of bullet mass to the square of its diameter. Generally, the higher the sectional density, the better the penetration of the bullet in living tissue. The sectional density of the FMJ 230-grain .45 ACP bullet is .162; for the 124-grain 9mm NATIO bullet, the figure is .144. By this traditional method of establishing a bullet’s terminal effectiveness, the .45 is again superior to the 9mm when both projectiles are of the FMJ type. By any mathematical calculation, given equal penetration, the .45 ACP bullet will create an approximately 40% greater permanent would cavity volume than a 9x19mm bullet. These mathematical predictions are borne out by actual testing, such as the FBI ammunition tests alluded to earlier.

To return to the FBI test protocols, it will be remembered that in penetration tests the .45 ACP FMJ scored 100%, while the 9mm achieved a slightly lower 95.5% success rate. While the minimum acceptable penetration for police use was established to be 12 inches, the FBI tests concluded that a penetration of 18 inches was even better. During the tests, however, the FBI assigned no points for penetration beyond the optimum 18 inches. The .45 ACP FMJ bullets penetrated an average depth of greater than 28 inches, while 9x19mm FMJ bullets were a full 4 inches less. Some might consider this over penetration, but for military applications, greater penetration is both acceptable and desirable. As previously mentioned, penetration is only one aspect of bullet effectiveness. The size of the permanent wound cavity must also be considered, and the .45 ACP FMJ bullets in the FBI tests achieved average permanent wound cavities of 3 cubic inches, while the 9mm bullet permanent wound cavities were a full cubic inch less. This significantly increases the prospect of the .45 striking a bone or internal organ. This can be summed up in the FBI’s overall wound value that assigns a value of 2.91 to the military .45 ACP and only 1.65 to the M882 9x19mm. This value is “... the index of demonstrated wounding effectiveness, not potential, as measured by the FBI Ammunition Test results.”

Another FBI study is more revealing as pertains to the actual “knockdown power” of the respective bullets. The term “knockdown power” is largely a myth, as already explained. The actual striking power of a given bullet at muzzle velocity is equal to its recoil. At any appreciable distance from the gun’s muzzle, the real striking power is appreciably less. To put this in perspective, it is instructive to note the height at which a weight must be dropped to equal the striking power of 9x19mm and .45 ACP bullets.

To equal the impact of a 9mm bullet at its muzzle velocity, a one pound weight must be dropped from a height of 5.96 feet, achieving a velocity of 19.6 fps. To equal the impact of a .45 ACP bullet, the 1-pound weight needs a velocity of 27.1 fps and must be dropped from a height of 11.4 feet. The dramatic difference between 9mm and .45 bullets in this test can be directly applied to their relative effect on the human body and partially explains why the 9x9mm is less effective than the .45 ACP for military applications when both bullets are of the FMJ variety. Thus, in terms of both wounding effectiveness and measured impact, the .45 ACP is superior to the 9x19mm.

In summation, the military handgun today, save for special applications and last ditch personal defense, is of little significance. Even for special operations use, it is not the primary weapon of any individual. In the days of horse cavalry, the handgun was an adjunct to the trooper’s saber and carbine, not his primary weapon. In today’s military, the handgun is usually the weapon of last resort. This is reflected in the current “personal defense weapon” nomenclature sometimes applied to handguns in lieu of the term pistol. That said, the term “personal defense weapon” is generally an over complication of a relatively simple term that more correctly alludes to the true purpose of the handgun - self-defense. The prudent solider or Marine will never plan on attacking or defending himself armed only with a handgun. His sidearm is the primary defense against unexpected attack or when his other weapons are either out of ammunition or unavailable. The foregoing notwithstanding, the sidearm carried by our military forces should be as lethal as possible.

With this in mind, selecting a cartridge for the military handgun should have two fundamental criteria: penetration and permanent wound cavity. A tertiary criterion is absolute striking power. Penetration is necessary because the handgun bullet must penetrate deeply enough to hit vital organs from less than optimum angles. The largest possible permanent wound cavity is required so as to cause the maximum amount of tissue destruction and concomitant hemorrhaging. Striking power is a requirement because the bullet must transfer the maximum amount of energy into the target. The larger bullet will damage blood vessels and organs that the smaller bullet closely misses. It will also arguably lead to more rapid blood loss than the smaller projectile. As previously stated, the .45 ACP causes a significantly larger permanent would cavity than the 9x19mm, and penetrates more deeply into the human body. Finally, as shown above, the absolute striking power of the .45 ACP is significantly greater than current military 9x19mm ammunition.

By all measures, the superiority of the .45 ACP over the 9x19mm for military use has been proven and is generally accepted by most small arms experts. It is also reflected in the data presented herein. The .45 ACP’s superiority is further established in the USSOCOM JSOR which, based upon independent analysis, specified a handgun of .45 caliber for several reasons, primarily because the .45 offers the greatest lethality. This being the case for special operations forces, it begs the question of whether or not the same criteria used to establish the superiority of the .45 ACP for special operations pistols should not also be used for general issue military handguns.


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