Handgun Wounding Factors: An Effectiveness Guide for Law Enforcement
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The handgun is the primary weapon in law enforcement – its purpose to apply deadly force to protect the life of the officer, the lives of others and to prevent serious physical harm. When an officer shoots a subject, it’s done with the explicit intention of immediately incapacitating that subject in order to stop whatever threat to life or physical safety is posed. The concept of immediate incapacitation is the only goal of any law enforcement shooting and is the underlying rationale for decisions regarding weapons, ammunition, calibers and training.
Because a lot is at stake when an officer is required to use his handgun, the selection of effective ammunition for law enforcement is a critical and complex issue. The issue is made even more complex by the amount of credible research and the wealth of uninformed opinion regarding what is commonly referred to as "stopping power." But in reality, few people have conducted relevant research in this area, and even fewer have produced credible information that is useful for law enforcement agencies in making informed decisions.
This article brings together what is believed to be the most credible information regarding wound ballistics from studies conducted by the FBI’s Firearms Training Academy in legendary Quantico, Virginia. It cuts through the confusion, and provides common-sense, scientifically supported principles by which the effectiveness of law enforcement ammunition may be measured. And while it’s not the final word on wound ballistics, it’s an important contribution to what should be an ongoing discussion.
Shot placement is an important, and often cited, consideration regarding the suitability of weapons and ammunition. However, considerations of caliber are equally important and cannot be ignored. For example, a bullet through the central nervous system with any caliber of ammunition is likely to be immediately incapacitating. Even a .22 rimfire penetrating the brain will cause immediate incapacitation in most cases. Obviously, this does not mean the law enforcement agency should issue .22 rimfires and train for head shots as the primary target. The realities of shooting incidents prohibit such a solution.
Few, if any, shooting incidents will present the officer with an opportunity to take a careful, precisely aimed shot at the subject’s head. Rather, shootings are characterized by several factors:
- Sudden, unexpected occurrence
- Rapid and unpredictable movement of both officer and adversary
- Limited and partial target opportunities
- Poor light and unforeseen obstacles
- The life-or-death stress of sudden, close, personal violence.
Training is oriented toward "center of mass" shooting. Proper shot placement is a hit in the center of the adversary, regardless of anatomy or angle. A review of law enforcement shootings clearly suggests that regardless of the number of rounds fired in a shooting, only one or two solid torso hits can be expected. This expectation is realistic because of the nature of shooting incidents and the extreme difficulty of shooting a handgun with precision under such dire conditions.
The probability of multiple hits with a handgun is not high. Experienced officers implicitly recognize that fact, and when potential violence is reasonably anticipated, their preparations are characterized by obtaining as many shoulder weapons as possible. Since most shootings are not anticipated, the officer involved cannot be prepared in advance with heavier armament. As a corollary tactical principle, no law enforcement officer should ever plan to meet an expected attack armed only with a handgun.
Nevertheless, a majority of shootings occur in circumstances in which the officer either does not have any other weapon available, or cannot get to it. The handgun must be relied upon, and must prevail. Given the idea that one or two torso hits can be reasonably expected in a handgun shooting incident, the ammunition used must maximize the likelihood of immediate incapacitation.
In order to predict the likelihood of incapacitation with any handgun round, an understanding of the mechanics of wounding is necessary. There are four components of projectile wounding. Not all of these components relate to incapacitation, but each of them must be considered. They are:
- Penetration: The tissue through which the projectile passes, and which it disrupts or destroys.
- Permanent Cavity: The volume of space once occupied by tissue that has been destroyed by the passage of the projectile. This is a function of penetration and the frontal area of the projectile. Quite simply, it is the hole left by the passage of the bullet.
- Temporary Cavity: The expansion of the permanent cavity by stretching due to the transfer of kinetic energy during the projectile’s passage.
- Fragmentation: Projectile pieces or secondary fragments of bone which are impelled outward from the permanent cavity and may sever muscle tissues, blood vessels, etc., apart from the permanent cavity. Fragmentation is not necessarily present in every projectile wound. It may or may not occur and can be considered a secondary effect.
Projectiles incapacitate by damaging or destroying the central nervous system, or by causing lethal blood loss. To the extent the wound components cause or increase the effects of these two mechanisms, the likelihood of incapacitation increases. Because of the impracticality of training for head shots, this examination of handgun wounding relative to law enforcement use is focused upon torso wounds and the probable results.
All handgun wounds will combine the components of penetration, permanent cavity, and temporary cavity to a greater or lesser degree. Fragmentation, on the other hand, does not reliably occur in handgun wounds due to the relatively low velocities of handgun bullets. Fragmentation occurs reliably in high-velocity projectile wounds (impact velocity in excess of 2,000 feet per second) inflicted by soft or hollow point bullets. In such a case, the permanent cavity is stretched so far, and so fast, that tearing and rupturing can occur in tissues surrounding the wound channel, which were weakened by fragmentation damage. It can significantly increase damage in rifle bullet wounds.
Since the highest handgun velocities generally do not exceed 1,400 to 1,500 feet per second (fps) at the muzzle, reliable fragmentation could only be achieved by constructing a bullet so frangible as to eliminate any reasonable penetration. Unfortunately, such a bullet will break up too fast to penetrate to vital organs. The best example is the Glaser Safety Slug, a projectile designed to break up on impact and generate a large, shallow temporary cavity. The estimated survival time of someone shot in the front mid-abdomen with a Glaser slug is about three days.
In cases where some fragmentation has occurred in handgun wounds, the bullet fragments are generally found within one centimeter of the permanent cavity. It is obvious that any additional wounding effect caused by such fragmentation in a handgun wound is inconsequential. Of the remaining factors, temporary cavity is frequently, and grossly, overrated as a wounding factor when analyzing wounds. Nevertheless, historically it has been used in some cases as the primary means of assessing the wounding effectiveness of bullets.
The most notable example is the Relative Incapacitation Index (RII) which resulted from a study of handgun effectiveness sponsored by the Law Enforcement Assistance Administration (LEAA). In this study, the assumption was made that the greater the temporary cavity, the greater the wounding effect of the round. This was based on a prior assumption that the tissue, bounded by the temporary cavity, was damaged or destroyed.
In the LEAA study, virtually every handgun round available to law enforcement was tested. The temporary cavity was measured, and the rounds were ranked based on the results. The depth of penetration and the permanent cavity were ignored. The result according to the RII is that a bullet which causes a large, shallow temporary cavity incapacitates more effectively than a bullet that causes a smaller temporary cavity with deep penetration.
Such conclusions ignore the factors of penetration and permanent cavity. Since vital organs are located deep within the body, it should be obvious that to ignore penetration and permanent cavity is to ignore the only proven means of damaging or disrupting vital organs. Further, the temporary cavity is caused by the tissue being stretched away from the permanent cavity, not being destroyed. By definition, a cavity is a space in which nothing exists. A temporary cavity is only a temporary space caused by tissue being pushed aside. That same space then disappears when the tissue returns to its original configuration.
Frequently, forensic pathologists cannot distinguish the wound track caused by a hollow point bullet (large temporary cavity) from that caused by a solid bullet (very small temporary cavity). There may be no physical difference in the wounds. If there is no fragmentation, remote damage due to temporary cavitation may be minor, even with high velocity rifle projectiles.
In the case of low-velocity missiles, the bullet produces a direct path of destruction with very little lateral extension within the surrounding tissues (e.g., pistol bullets). Only a small temporary cavity is produced. To cause significant injuries to a structure, a pistol bullet must strike that structure directly. The amount of kinetic energy lost in tissue by a pistol bullet is insufficient to cause remote injuries produced by a high-velocity rifle bullet.
The reason is that most tissue in the human target is elastic in nature. Muscle, blood vessels, lungs, bowels – all are capable of substantial stretching with minimal damage. Studies have shown that the outward velocity of the tissues in which the temporary cavity forms is no more than one tenth of the velocity of the projectile. This is well within the elasticity limits of tissue – such as muscle, blood vessels, and lungs. Only inelastic tissue like liver, or the extremely fragile tissues of the brain, would show significant damage due to temporary cavitation.
The tissue disruption caused by a handgun bullet is limited to two mechanisms:
This is the hole the bullet makes passing through the tissue. Of the two, the crush mechanism, the result of penetration and permanent cavity, is the only handgun wounding mechanism which damages tissue. To cause significant injuries to a structure within the body using a handgun, the bullet must penetrate the structure. Temporary cavity has no reliable wounding effect in elastic body tissues. Temporary cavitation is nothing more than a stretch of the tissues, generally no larger than 10 times the bullet diameter (in handgun calibers), and elastic tissues sustain little, if any, residual damage.
This is the temporary cavity formed by the tissues being driven outward in a radial direction away from the path of the bullet.
With the exceptions of hits to the brain or upper spinal cord, the concept of reliable and reproducible immediate incapacitation of the human target by gunshot wounds to the torso is a myth. The human target is a complex and durable one. A wide variety of psychological, physical, and physiological factors exist, all of them pertinent to the probability of incapacitation. However, except for the location of the wound and the amount of tissue destroyed, none of the factors are within the control of the law enforcement officer.
Physiologically, a determined adversary can be stopped reliably and immediately only by a shot that disrupts the brain or upper spinal cord. Besides a hit to the central nervous system, massive bleeding from holes in the heart or major blood vessels of the torso causing circulatory collapse are the only other ways to force incapacitation upon an adversary, and this takes time. For example, there is sufficient oxygen within the brain to support full, voluntary action for 10 to 15 seconds after the heart has been destroyed.
- Physiological factors may actually play a relatively minor role in achieving rapid incapacitation.
- Barring central nervous system hits, there is no physiological reason for an individual to be incapacitated by even a fatal wound, until blood loss is sufficient to drop blood pressure and/or the brain is deprived of oxygen.
- The effects of pain, which could contribute greatly to incapacitation, are commonly delayed in the aftermath of serious injury such as a gunshot wound.
- Due to survival patterns, like the well-known "fight or flight" syndrome, pain is irrelevant to survival and is commonly suppressed.
- Pain must first be perceived and then must cause an emotional response. In many individuals, the response is anger and increased resistance, not surrender.
Psychological factors are probably the most important relative to achieving rapid incapacitation from a gunshot wound to the torso. This can include:
- Awareness of the injury (often delayed by the suppression of pain)
- Fear of injury, death, blood, or pain
- Intimidation by the weapon or the act of being shot
- Preconceived notions of what people do when they are shot
- The simple desire to quit can
These can all lead to rapid incapacitation, even from minor wounds. However, psychological factors are also the primary cause of incapacitation failures. Here are ways this can happen:
- The individual may be unaware of the wound and thus has no stimuli to force a reaction.
- Strong will, survival instinct, or sheer emotion such as rage or hate can keep a grievously injured individual fighting, as is common on the battlefield and in the street.
- The effects of chemicals can be powerful stimuli preventing incapacitation.
- Adrenaline alone can be sufficient to keep a mortally wounded adversary functioning.
- Stimulants, anesthetics, painkillers, or tranquilizers can all prevent incapacitation by suppressing pain, awareness of the injury, or eliminating any concerns over the injury.
- Drugs such as cocaine, PCP, and heroin are dis-associative in nature. One of their effects is that the individual "exists" outside of his body. He sees and experiences what happens to his body, but as an outside observer who can be unaffected by it yet continue to use the body as a tool for fighting or resisting.
The often referred to "knock-down power" implies the ability of a bullet to move its target. This is nothing more than momentum of the bullet, causing a target to move in response to the blow received. In order 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 .45ACP bullet, the one-pound weight needs a velocity of 27.1 fps and must be dropped from a height of 11.4 feet. A ten-pound weight equals the impact of a 9mm bullet when dropped from a height of 0.72 inches (velocity attained is 1.96 fps), and equals the impact of a .45 when dropped from 1.37 inches (achieving a velocity of 2.71 fps).
A bullet simply cannot knock a man down. If it had the energy to do so, then equal energy would be applied against the shooter and he too would be knocked down. This is simple physics, as the amount of energy deposited in the body by a bullet is approximately equivalent to being hit with a baseball. Tissue damage is the only physical link to incapacitation within the desired time frame – which is instantaneously.
The critical wounding components for handgun ammunition, in order of importance, are penetration and permanent cavity. The bullet must penetrate sufficiently to pass through vital organs and be able to do so from less than optimal angles. For example, a shot from the side through an arm must penetrate at least 10 to 12 inches to pass through the heart. A bullet fired from the front through the abdomen must penetrate about seven inches in a slender adult, just to reach the major blood vessels in the back of the abdominal cavity. Penetration must be sufficiently deep to reach and pass through vital organs, and the permanent cavity must be large enough to maximize tissue destruction and consequent hemorrhaging.
Several design approaches have been made in handgun ammunition, which are intended to increase the wounding effectiveness of the bullet. Most notable of these is the use of a hollow point bullet designed to expand on impact.
Expansion accomplishes several things. On the positive side, it increases the frontal area of the bullet and thereby increases the amount of tissue disintegrated in the bullet’s path. On the negative side, expansion limits penetration. It can prevent the bullet from penetrating to vital organs, especially if the projectile is of relatively light mass, and the penetration must be through several inches of fat, muscle, or clothing.
Increased bullet mass will increase penetration. Increased velocity will increase penetration, but only until the bullet begins to deform, at which point increased velocity decreases penetration. Permanent cavity can be increased by the use of expanding bullets, and/or larger diameter bullets, which have adequate penetration. However, in no case should selection of a bullet be made where bullet expansion is necessary to achieve desired performance. Bullet selection should be determined based on penetration first, and the unexpanded diameter of the bullet second, as that is all the shooter can reliably expect. Here’s why:
- Damage to the hollow point by hitting bone, glass, or other intervening obstacles can prevent expansion.
- Clothing fibers can wrap the nose of the bullet in a cocoon like manner and prevent expansion.
- Insufficient impact velocity caused by short barrels and/or longer range will prevent expansion, as will simple manufacturing variations.
It is essential to bear in mind that the single most critical factor remains penetration – a handgun bullet must reliably penetrate 12 inches of soft body tissue at a minimum, regardless of whether it expands or not. If the bullet does not reliably penetrate to these depths, it is not an effective bullet for law enforcement use.
An issue that must be addressed is the fear of over-penetration widely expressed on the part of law enforcement. The concern that a bullet would pass through the body of a subject and injure an innocent bystander is clearly exaggerated. Any review of law enforcement shootings will reveal that the great majority of shots fired by officers do not hit any subjects at all. It should be obvious that the relatively few shots that do hit a subject are not somehow more dangerous to bystanders than the shots that miss the subject entirely.
Choosing a bullet because of relatively shallow penetration will seriously compromise weapon effectiveness, and needlessly endanger the lives of the law enforcement officers using it. No law enforcement officer has lost his life because a bullet over-penetrated his adversary. On the other hand, tragically large numbers of officers have been killed because their bullets did not penetrate deeply enough.
There is no valid, scientific analysis of actual shooting results in existence, or being pursued to date. There are some well-publicized, so-called analyses of shooting incidents being promoted, however, that are greatly flawed.
These so called studies are further promoted as being somehow better and more valid than the work being done by trained researchers, surgeons and forensic labs. They disparage laboratories, claiming that the "street" is the real laboratory and their collection of results is the real measure of caliber effectiveness, as interpreted by them, of course. Yet their data from the street is collected haphazardly, lacking scientific method and controls, with no noticeable attempt to verify the less-than-reliable accounts of the participants with actual investigative or forensic reports.
Further, it appears that many people are predisposed to fall down when shot. This phenomenon is independent of caliber, bullet, or hit location, and is beyond the control of the shooter. Given this predisposition, the choice of caliber and bullet is essentially irrelevant. The causing factors are most likely psychological in origin – thousands of books, movies and television shows have educated the general population that when shot, one is supposed to fall down.
The reason for seeking a better cartridge for incapacitation is that individual who is not predisposed to fall down. If a bullet destroys about two ounces of tissue in its passage through the body, that represents 0.07 of one percent of the mass of a 180-pound man. And while it may certainly be lethal, a body count is no evidence of incapacitation. More people in this country have probably been killed by .22 rimfires than all other calibers combined – which, based on body count, would compel the use of .22s for self-defense. But, more importantly, what did the individual do when hit?
Many other questions are left unanswered when trying to assess calibers by small numbers of shootings:
- What percentage of those stops were preordained by the target?
- How many of those targets were not at all disposed to fall down?
- How many multiple shots failed to stop?
- What is the definition of a stop?
- What did the successful bullets hit and what did the unsuccessful bullets hit?
- How many failures were in the vital organs, and how many were not? How many of the successes?
- What is the number of the sample?
- How were the cases collected?
- What verifications were made to validate the information?
- How can the verifications be checked by independent investigation?
Because of the extreme number of variables within the human target, and within shooting situations in general, even a hundred shootings is statistically insignificant. If anything can happen, then anything will happen. Large sample populations are absolutely necessary.
Although no cartridge is certain to work all the time, surely some will work more often than others, and any edge is desirable in one’s self defense – this is simple logic. It is safe to assume that if a target is always 100-percent destroyed, then incapacitation will also occur 100-percent of the time. If 50 percent of the target is destroyed, incapacitation will occur less reliably. The round which destroys 0.07 percent of the target will incapacitate more often than the one which destroys 0.04 percent. However, only very large numbers of shooting incidents will prove it. The difference may be only 10 out of a thousand, but that difference is an edge, and that edge should always be on the officer’s side.
Those who disparage science and laboratory methods are either too short sighted or too bound by preconceived (or perhaps proprietary) notions to see the truth. The labs and scientists do not offer sure things. They offer a means of indexing the damage done by a bullet, understanding of the mechanics of damage caused by bullets and the actual effects on the body, and the basis for making an informed choice based on objective criteria and significant statistics.
Any shooting incident is a unique event, unconstrained by any natural law or physical order to follow a predetermined sequence of events or end in predetermined results. Physiologically, no caliber or bullet is certain to incapacitate any individual unless the brain is hit. Psychologically, some individuals can be incapacitated by minor or small caliber wounds. Those individuals who are stimulated by fear, adrenaline, drugs, alcohol, and/or sheer will and survival determination may not be incapacitated, even if mortally wounded.
Kinetic energy does not wound. Temporary cavity does not wound. The bullet must pass through the large, blood-bearing organs and be of sufficient diameter to promote rapid bleeding. Penetration less than 12 inches is too little – and "too little penetration will get you killed."