- "An Alternate Look at Handgun Stopping Power"--Greg Ellifritz at Buckeye Firearms Association (2011). This is Greg's original article describing and analyzing his research into real world shootings, which was used in the video above. Ellifritz conducted his research because of criticisms or concerns of a similar study conducted by Evan Marshall. Specifically, Ellifritz notes his criticism of Marshall's study:
For consistency purposes, they ONLY included hits to the torso and ONLY included cases where the person was hit with just a single round. Multiple hits screwed up their data, so they excluded them. This led to an unrealistically high stopping power percentage, because it factored out many of the cases where a person didn't stop! I wanted to look at hits anywhere on the body and get a realistic idea of actual stopping power, no matter how many hits it took to get it. So I started collecting data.
The main takeaway from Greg's study is that the popular self-defense cartridges (.380, .38 Special, 9 mm, .357 Mag., .40 S&W, .45 ACP) perform about the same. Although the smaller calibers (.22, .25, and .32) can perform as well as the larger calibers with an accurate hit to a vital zone, their failure rate (i.e., failure to stop an attack) is much higher than the larger calibers. (See also "DEFENSIVE CARRY: CALIBER AND INCAPACITATION"--The Daily Caller. This is a 2013 article by Ellifritz on the same topic, but it raises the point that there are three methods by which an aggressor is stopped by bullet impacts: psychological stop, central nervous system, and blood loss).
- "Handgun Ammunition Stopping Power Update"--Evan Marshall (2004). In this article, Marshall summarizes his research of the results of real world shootings. Marshall only focused on one-shot stops. He explains:
For the purposes of this study, a “stop” is defined as: 1) one shot to anywhere on the torso, not counting head, neck or extremity shots; 2) where the subject stops shooting, if he was shooting, or stops striking blows, if that is what he was doing; and 3) runs no more than 10 feet, if he runs. This study only deals with what happens in the first few seconds after the shooting, and does not factor in the eventual lethality of the wound or total recovery from the wound.
One of the useful features of Marshall's study is that he breaks down his data by particular brands and loads, so, for instance, you can compare Cor Bon versus Gold Dot for the same caliber. Based on his data, the top performers are 9mm, .357 Mag., .357 Sig, .40 S&W, and .45 ACP. According to his data, the .32 ACP, .38 Special, and .380 ACP are of similar effectiveness, but much less effective than the top performers.
- "The Strasbourg Tests" (PDF). The article explains that "[t]he Strasbourg Tests were initiated on the strength of the premise that briefly amplified systemic pressure of a specific magnitude can cause disorientation and loss of consciousness." The subjects were goats of 155 to 165 pounds. Autopsies were also performed. The key information was the Average Incapacitation Time (AIT) of specific calibers. Per the article, "[a]n animal was deemed 'incapacitated' if it collapsed and was unable to rise to a standing position." There are tables at the end of the report setting out results for specific brands and types of rounds for each caliber. Basic results, looking at overall performance, show that .380 ACP and .38 Special (out of a 2-inch barrel) were about the same; 9 mm, .40 S&W, and .45 APC had comparable performance; and 10 mm and .357 Magnum were fairly comparable. However, there was considerable difference between different rounds for the same caliber that was greater than the difference between the averages between different calibers. In other words, according to this test, bullet design, velocity and power can be as much or more important than caliber (note, however, that all the ammunition tested was .355 or larger).
- "Handgun Cartridge Power Chart"--Chuck Hawks. This summarizes findings from ballistic gel tests, Marshall's study, and the Strasbourg goat test.
- "THE MILITARY EFFECTIVENESS OF PISTOL CARTRIDGES: AN ANALYSIS OF THE .45 ACP VERSUS THE 9X19MM IN MILITARY SERVICE"--by Charles Q. Cutshaw at Small Arms Review. This article is probably of more limited use for the civilian shooter because it only looks at the effectiveness of FMJ (Ball) rounds. It is interesting because it discusses the testing conducted by the military prior to the adoption of the .45 ACP. A few other interesting points on wounding:
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.”
The author concludes that, when using FMJ ammunition, the .45 ACP is superior to the 9 mm, explaining:
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.
- "Handgun Wounding Factors: An Effectiveness Guide for Law Enforcement"--Ammo.com. This article presents a different list of wounding mechanics:
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.
Specific mechanisms of injury are through crushing (e.g., permanent cavity) and stretching (e.g., temporary cavity). The articles also notes that a gunshot wound can cause a psychological stop because the aggressor gives up after being shot. This article also offers up criticism of studies based on shooting incident results, such as Marshall's and Ellifritz's studies, reasoning:
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 author offers several conclusions, including this:
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."
- "Handgun Wounding Factors and Effectiveness"--This is a July 1989 report prepared by the FBI, and apparently was the basis of the Ammo.com article cited directly above.
- "Handgun Self-Defense Ammunition Ballistics Test"--Lucky Gunner Ammo. Probably the largest collection of ballistic gelatin test results on the Internet.
- "The Ballistic Pressure Wave Theory of Handgun Bullet Incapacitation" (PDF)--Michael Courtney and Amy Courtney. This article addresses stress waves or amplified systemic pressure, as discussed in other articles, as a means of disabling a target. I would note that this theory is controversial simply because it adds a wounding factor that was not considered by Martin L. Fackler. From the introduction of the article:
Debates in terminal ballistics such as light-and fast vs. slow-and-heavy debates are dramatic oversimplifications of the more scientific question of whether the wound channel (directly crushed tissue) is the only contributor to handgun bullet effectiveness or whether a more energy dependent parameter such as hydrostatic shock, the temporary stretch cavity, or ballistic pressure wave can also contribute.
These debates have been dominated by longwinded rhetoric and authoritative appeals rather than scientific data and analysis. Here, we summarize findings that support and quantify the pressure wave hypothesis:
Other factors being equal, bullets producing larger pressure waves incapacitate more rapidly than bullets producing smaller pressure waves.
The pressure wave hypothesis is supported by:
1) Pressure pulses inducing incapacitation and brain injury in laboratory animals.
2) Ballistic pressure waves originating remotely from the brain causing measurable brain injury in pigs and dogs.
3) Experiments in animals showing the probability of rapid incapacitation increases with peak pressure wave magnitude.
4) Epidemiological data showing that the probability of incapacitation increases with the peak pressure wave magnitude.
5) Brain damage occurring without apenetrating brain injury in a human case study.
6) Ballistic pressure waves causing spinal cord injuries in human case studies.
7) Blast waves causing brain injury without penetrating injury or blunt force trauma.
(Citations omitted). The Courtneys have additional research and articles that you can find online. While they in no way argue that this is the only, or even most significant wounding effect, it does provide a mechanical explanation, for instance, of the results of the Strasbourg test where certain light weight rounds that didn't have much penetration (e.g., Glaser safety rounds) caused rapid incapacitation.
- "Have No Faith in Your Defensive Handgun Caliber or Load! (Or Why I don’t Get Involved in “Caliber Wars.”)" by Stephen A. Camp at The Snubnose Files. Lots of good information in this article, but the take-away is: "Once you have a caliber capable of adequate penetration and expansion, placement is power."
- "Concealed Carry: Is The .380 ACP Enough For Self-Defense?"--Gun Digest. I only include this article because of this tidbit:
In 2006, a coroner wrote a report titled, “Terminal Ballistics as Viewed in a Morgue.” [Dr. Andreas Grabinsky] stated he performed an average of 8.2 autopsies a day and chose to be blunt in his findings. “I absolutely despise a 9mm for defensive situations … and a .380 ACP as well,” he wrote, adding he will “take a slow-moving .45 ACP to a gunfight any day.” In addition, he stated that when a gunshot wound victim crossed his autopsy table with multiple rounds in their bodies, those bullets were typically .380 ACP or 9mm, while single-shot gunshot wound victims were usually shot by .40 S&W or .45 ACP.
- "Stopping Power – One Doctor’s Point of View"--The Truth About Guns. The author's take:
I should probably write something more organized about this, but I wanted to share these articles in the interim.
My advice (or reasoned speculation) is get a gun that you like and will carry around with you. Since what little data there is suggests that guns usually stop the festivities without pulling the trigger 50 or 100 times for every time they actually are fired, don’t get too lathered up about what caliber it is. More important is that it’s comfortable and that you like it, and will actually use it. A .22 in your hand is better than a .45 at home. View the advice you receive at the gun store or from cops with healthy skepticism. I was the kid behind the counter at a really good gun store back in the day, and I can assure you that we didn’t know the answers. Some of the biggest, most egregious whoppers I’ve ever heard floated across counters at gun stores. And cops…never mind.
More importantly, get your mind off of stopping power and onto fighting. That’s what your gun is for, and it’s what you’ll be doing even if your gun doesn’t work. They don’t always. Most of us would be safer with some generic training in tactics and strategy for everyday life instead of blasting away at hanging paper, fun as it is.