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Thoughts on Handgun Stopping Power

A Question About Stopping Power

I was teaching last month and the issue of stopping power came up; why would someone go with a 9mm when they can have a .40… or a .45? This question led to a Saturday morning resurrection of the caliber waI had to throw my two cents in.(My observations are based largely memory of events of the day, a time before the internet, so I can’t go back and do the research). For what it’s worth, this is my take on it.

The Birth of the Caliber War

In 1978 Jeff Cooper and Bill Jordan were icons of the gun scene and Guns and Ammo magazine was the king of the gun press. In defensive handguns the revolver still dominated law enforcement. In the handgun circles Cooper preached the .45 ACP, Jordan the .357 Magnum, but for the everyday working cop, the 38 special was still the overwhelming the handgun of choice by departments and because of this, most of the American public embraced the 38 as well. That distinction was quickly slipping away as law enforcement agencies one after another, began to transition to the auto-loading 9mm pistol. As they did, all eyes were on the success or failure of the 9mm in this role. To the surprise of everyone the 9mm as a fighting caliber appeared to be surpassing all expectations in performance and stopping power and thus was born the term “wonder nine”. A name given to this new generation of 9mm high performance ammo by gun writers of the day to assert that the terminal ballistic effect of a modern bullet design could surpass conventional 38 Special, .357 magnum and even the venerable old .45 ACP bullets in stopping power, an opinion largely unsupported by the science. This informal data collecting further lead to the “one shot stop ratio”, a completely fabricated statistic that gun magazine writers promoted and used to sell magazines and advertiser products. The war was on, the .357 magnum guys waived data sheets in dispute, the .45 auto guys felt an argument in the matter was below them; this was the Genesis of the caliber war which would last for over 30 years. Nevertheless, the move by law enforcement to transition was on.

By 1990 most law enforcement agencies around America had seen the light and took the plunge with the 9mm, but after the honeymoon was over, duty officer performance with the 9mm autoloader began to taper off and fall back to the revolver levels of previous years. It turns out that the 9mm wasn’t the performer that everyone thought it was. Several critical incidents lead law enforcement to doubt the performance of the 9mm and began to look elsewhere.

Never being a big fan of the .45 ACP, agencies like the FBI initially jumped on the new 10mm, but were eventually wooed by the ammo companies away from the 9mm and 10mm taking the Goldilocks approach. The 9mm was way too soft and the 10mm was way too harsh, but the .40 Smith and Wesson was… just right. The .40 Smith & Wesson was born out of compromise, a solution to a problem that really didn’t exist; most thought the caliber war was over and the .40 Smith & Wesson had won.

SAAMI Spoke Up

Years later I read in a periodical article from I think, SAAMI (Sporting Arms Ammunition Manufactures Institute). The purpose of the article was to explain to professionals in the industry, the sudden love affair with the 9mm stopping power and how it significantly outperformed the 38 special when, from a ballistics stand point, they’re very close to being equal. Folks in the industry knew that there was a lot of junk science flying around in the periodicals; the purpose of their study was to set the record straight and to return a little logic to the study of ammunition performance. To do that, they had to venture out of the clinical study of terminal ballistics and venture into the world of the end user. Their findings were as follows:

  1. Agencies or units that were early to transition to the 9mm tended to be well funded, well equipped and well trained. Those agencies that were properly trained consistently outperformed others, regardless of the weapon or caliber type.
  2. Transition from the revolver to the auto entailed an in-service ground up training approach which allotted a generous amount of training time and ammo for the transition purposes. Typically, an officer attending semi-annual service revolver qualification would be issued a box of fifty rounds, would qualify and in and in an hour or so, be sent on their way. However, in the transition from revolver to autoloader process an officer would have five hundred or more rounds available for training purposes and the officer would spend two to three days of intense training. This would result in a training based skill and ability spike. When complete, the officer will be at the top of their game in confidence, skill and ability. This skill is however, perishable and as was seen, skill levels soon dropped back to pre 9mm levels once officers returned to their normal requalification cycle.
  3. Specialized units that receive the most up to date in training and tactics outperform the line staff regardless of caliber.

Based on the factors above, the difference in performance was not a terminal ballistics issue, it was  a training issue, but the move was on.

The FBI Speaks Up

By 2010 agencies that adopted the 40 S&W were gradually reverting back to the 9mm. In 2014 the FBI Training Division, FBI Academy, Quantico, VA. seemed to nail the lid shut in the caliber debate with their Executive Summary as follows:

  • Most of what is “common knowledge” with ammunition and its effects are rooted in myth and folklore.
  • The single most important factor in effectively wounding a human target is to have penetration to a scientifically valid depth (12” – 18”).
  • LEO’s miss between 70 – 80 percent of the shots fired during a shooting incident!
  • 9mm Luger now offers select projectiles which are, under identical testing conditions, outperforming most of the premium line .40 S&W and .45 Auto projectiles tested by the FBI.
  • 9mm Luger offers higher magazine capacities, less recoil, lower cost (both in ammunition and wear on the weapons) and higher functional reliability rates (in FBI weapons).
  • There is little to no noticeable difference in the actual wound tracks between premium handgun projectiles from 9mm Luger through the .45 Auto.
  • Given contemporary bullet construction, LEO’s can field (with proper bullet selection) 9mm Lugers with all of the terminal performance potential of any other law enforcement pistol caliber, but with none of the disadvantages present with the larger straight wall case calibers.

In a different study conducted at the time, the effectiveness (stopping power) of various police munitions were studied and it was found that terminal ballistics of the individual pistol round had little difference in effectiveness. Cited in this study was the mutual understanding that the most effective police weapon of the time was the 12 gauge shotgun loaded with 00 Buck (each round containing nine .32 caliber lead balls). To the ballistics geeks out there, this was an interesting dichotomy. The high performance ammunition that manufactures were kicking out, that would squeak out the slightest edge in performance, could not come close to the top fight stopper in the police inventory. It was the 18th century .32 caliber lead musket ball, albeit… nine of them, all at once. What gives the 00 Buck (Nine .32 caliber lead balls) the defining edge over the modern pistol calibers? The 00 Buck round is capable of rapidly inflicting multiple traumas to as many vital organs, thus shutting down multiple systems all at once. Something a double tap just won’t do.

Think about that one.


The caliber war is over and the 9mm seems to have won. We can argue to no end about terminal ballistics and the edge one that caliber or bullet design has over the other, but in examining the ballistics throughout the entire spectrum of all commercially available munitions, the 9mm, .40 and .45 show very little difference. However, the ability to inflict wounds to multiple vitals, shutting them down simultaneously seems to be the key to stopping power.



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