Self-Defense: Is Stopping Power a Myth?

By Justin Stapley | Shooting Director


I’ve been a .40 S&W guy my whole life. My thought process has always been that it’s an excellent middle ground between the .45 ACP and the 9mm. The .40 S&W maintains a respectable level of power yet still allows increased ammo capacity and decreased recoil – and it has great stopping power.

Until a few years ago, my fellow shooting enthusiasts and firearms instructors supported this theory. In 2014, the FBI shocked everyone by announcing a return to the 9mm as their standard-issue round. For justification, the FBI pointed to in-house studies , documented in this FBI Executive Summary, which concludes that “Handgun stopping power is simply a myth.”

Since then, a lot of organizations and individual gun owners have adopted this mentality – that stopping power is a myth. The growing belief is that the only meaningful considerations for ammunition type are capacity, penetration, and light-recoil. I’m still a .40 S&W guy because I figured one study is one study. But I am often hard-pressed to defend myself against claims I’m sacrificing speed, accuracy, and ammo capacity with no benefit gained.

Eventually, I got serious and started trying to learn more about the FBI’s findings. I also did some heavy reading on traditional understandings about the idea of “stopping power.” In this article, I’ll lay out what I’ve found.

My Findings

While the FBI Executive Summary claims their findings debunked the idea of stopping power, that isn’t necessarily the proper conclusion to draw from their data.

The data, and the administrative assertions of the FBI, point to the reality that stopping power is and continues to be highly misunderstood. Many of the diverging opinions and conclusions surrounding the FBI findings result from different ideas of what stopping power is.

What is stopping power?

When the FBI Training Division said stopping power is a myth, and when marksmen and shooters repeat this claim, they’re defining stopping power as stopping somebody in their tracks, or even knocking them back. If this were what stopping power was, the FBI wouldn’t have needed to debunk it.

Every learned and knowledgeable marksman knows that the movie magic of somebody getting knocked back – when shot – as if kicked by a mule is laughable. And, most marksmen recognize that the chance of dropping an assailant dead with a single shot is highly improbable. It should be evident that stopping power means more than these ideas, or it wouldn’t be something serious marksmen have ever discussed.

Stopping power is better defined as the ability to effectively and swiftly incapacitate (stop) the assailant and end the altercation. More specifically, it relates to the combination of several ballistic factors, including tissue displacement and transfer of energy leading to trauma, shock, and hemorrhaging.

What the FBI findings actually point to is a conclusion that speed and accuracy play a much more substantial role in determining stopping power than was previously believed. Rapid and precise placement of small, high-speed projectiles to a lethal area has more stopping power than scattered and slower placement of large, low-speed projectiles.

Is it ammunition-based?

This is the part where the FBI Executive Summary and its defenders make too bold of a claim. The actual performance of various ammunition doesn’t point to stopping power being a myth; it points to a more accurate conclusion that a larger round does not grant more stopping power absent good training and marksmanship skills. If a marksman can place larger projectiles rapidly and precisely, then there is more tissue displacement, more transfer of energy, and more stopping power.

The reason the FBI, and other organizations that followed their lead, went back to the 9mm, truly relates less to the superiority of the round and more to the cost and logistics of effective and constant training. While the FBI Executive Summary claims differently, the reality of actual bullet performance indicates their decision related more to the cost of larger ammunition and the more advanced and in-depth marksmanship training required to get effective use out of larger rounds.

Ultimately, based on the history of ammunition development and stories of smaller projectiles proving to be less effective, what the FBI really concluded was that the modern improvements to the 9mm made it good enough. While the FBI Executive Summary declares the 9mm is superior and that stopping power is a myth, they don’t adequately back that up.

The ammunition performances they cite, the lack of insight they provide into the administrative decision process for abandoning the.40 S&W, and the history of ammunition development and use over the last century-and-a-half should make all marksmen cautious of accepting the assertion that “stopping power is simply a myth.”

Personally, the FBI study and the new debate about stopping power it unleashed informed me more about what it is – but it doesn’t force me to conclude that I should dump the .40 S&W.

As an individual, I have very different considerations when compared to a large organization. How much time do I dedicate to training? How natural are my marksmanship skills? What gun works best for concealment or feels good in my hand (and what ammunition options are there for that gun)? What kind of gun/ammunition did I grow up shooting? Do I flinch or anticipate when shooting? Am I “recoil sensitive”? Do I anticipate the recoil or have sympathetic grip reflexes in response to the feeling that the gun might fly out of my hand?

The definitive conclusions of the FBI Study are that shot placement is the underlying factor in lethality. So yes, all of the above considerations have a more significant impact on stopping power than the size of the bullet. If, for whatever reason, I can’t shoot fast and accurately with the weapon and ammunition I’m currently using, then yes, switching to a 9mm,.380 ACP, or other smaller caliber would grant me more stopping power than I currently have.

But this doesn’t mean bullet size doesn’t matter. If I can put three rapid shots on top of each other at ten yards or more with my .40 S&W than I do have more stopping power than someone who can only do the same thing with a smaller round.

In case you were wondering, I’m still a .40 S&W guy. Constant self-assessment has led me to conclude that my skill is good enough to allow my original thought process to remain relevant. But I am much more aware of the necessity to maintain my marksmanship while carrying a larger round.


Justin Stapley is the Shooting Director for Spencer Durrant Outdoors, and a political writer whose principles and beliefs are grounded in the idea of ordered liberty as expressed in the traditions of classical liberalism, federalism, and modern conservatism. His writing has been featured at the Federalist Coalition, the NOQ Report, and Porter Medium. He lives in Bluffdale, Utah, with his wife and daughters.