What Is the Best Caliber for Self-Defense?

By Fred Mastison
Posted in #EDC
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What Is the Best Caliber for Self-Defense?

December 17th, 2023

5 minute read

There are few debates in the firearms realm as passionate as those centered around ammo. Asking “what is the best self-defense caliber” is akin to asking who the best baseball player of all time is.

Opinions fly freely yet in the end, we have data to help us make the call as to which handgun caliber is most practical for concealed carry and personal protection.

Personal Defense Caliber Candidates

When we are talking about the best calibers for self-defense, there are several candidates from which to choose:

  • 9mm – A popular favorite, it offers a balance of power, capacity and modest recoil. Plus it can be found in a wide range of full-size and compact pistols.
  • .40 S&W – The .40 blasted to popularity in the 90s but began to fade a bit in recent years. It offers more power than the 9mm, but at the cost of increased recoil.
  • .45 ACP – With more than 100 years of experience, this cartridge is considered by many to be the ultimate man stopper.
  • 10mm – Once the darling of both the FBI and Miami Vice, the cartridge has a lot going for it, but it suffers from reduced capacity and stout recoil.
  • .380 ACP – Newer ammunition improves the tiny cartridge’s capabilities, but it still falls short of the other concealed carry options.

Handgun Stopping Power

First off, we need to address a term that is thrown about in the handgun world that simply needs to be taken out of the equation. This term is “stopping power.”

As a rule, handgun rounds lack sufficient power to merit a measurement in the stopping power category. Law enforcement data tells us that adversaries generally have to be shot multiple times before they back down from the fight or become incapacitated.

While rifle and shotgun rounds generate large wound channels, general defensive carry handguns do not provide enough power to knock a person out of a fight quickly unless it is a head shot or spinal shot.

While there are power differences between loads, the idea of identifying which pistol cartridge has the most stopping power is an irrelevant issue.

The Best Personal Protection Cartridge Is…

Drum roll please… the best self-defense caliber is the 9mm hollow-point round.

9mm personal defense ammunition

Yes, I know there are some 10mm and .45 ACP fans screaming right now, but science is a part of this statement.

Believe it or not, the FBI returned to the 9mm round after what seems like a circus tour of various calibers. From their initial use of 9mm to 10mm and .40 S&W, they have come full circle back to the 9mm. There are good reasons for this.

The reasons why the 9mm edges out the other calibers include:

  1. Penetration
  2. Terminal effectiveness
  3. Speed and controllability
  4. Capacity


The reason the 9mm reigns supreme is because it provides penetration to a scientifically valid depth. A projectile must penetrate deeply enough into the body to reach the large vital organs, namely heart, lungs, aorta, vena cava and to a lesser extent liver and spleen, in order to cause rapid blood loss.

It has long been established by expert medical professionals, experienced in evaluating gunshot wounds that this equates to a range of penetration of 12 to 18 inches, depending on the size of the individual and the angle of the bullet.

Terminal Effectiveness

This is the case because as the FBI states “contemporary projectiles (since 2007) have dramatically increased the terminal effectiveness of many premium line law enforcement projectiles.” This is something Eric Conn examined in his article “Anatomy of a Defensive Bullet” published here on The Armory Life.

The 9mm now outperforms most of the premium line .40 S&W and .45 ACP projectiles tested by the FBI. The big part of this is wound channels.

Shooting a Springfield 911 chambered for the 9mm

This is also where myth and science start to separate things. .45 ACP does indeed make bigger holes in paper than the 9mm, but flesh is not paper and wound channels close around bullet tracks. Surgeons have been asked and they report that there is little to no noticeable difference in the wound tracks between premium line law enforcement projectiles from 9mm and the .45 ACP.

One of the primary keys is the use of high performance projectiles. A top tier hollowpoint bullet like the Federal HST round will deliver consistent penetration and expansion for optimal performance.

When you consider how well the Norma MHP expands in gel, you can see that the best personal defense ammo of today is vastly improved when compared to that of 20 or 30 years ago.

Speed & Controllability

On a more logistical side, people are able to run a 9mm faster and more accurately than other larger calibers. A significant part of this comes from the cartridge having less felt recoil.

In a recent article on the .40 S&W cartridge, Tom McHale’s calculations show the 9mm can have 35%+ less recoil. With less recoil to manage, a shooter can get his sights back on target quickly.

Further, less recoil can lead to greater enjoyment of shooting. If you like shooting, it stands to reason that you will become more efficient with the pistol as you will choose to spend more time on the range.

This is always a win because time on trigger is critical to developing good defensive marksmanship skills.


The 9mm offers greater magazine capacity than virtually any other pistol caliber carried for personal defense. If the wounding capabilities of 9mm and the other cartridges are nearly identical, it would seem to be that having more rounds in you magazine will give you a better opportunity to stop an attacker.

Final Thoughts

While it probably breaks some people’s hearts, the 9mm round is the carry king regardless of what the social media memes might say.

Editor’s Note: Please be sure to check out The Armory Life Forum, where you can comment about our daily articles, as well as just talk guns and gear. Click the “Go To Forum Thread” link below to jump in and discuss this article and much more!

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Fred Mastison

Fred Mastison

Fred Mastison is a national magazine contributor, professional firearms & combatives instructor and executive protection provider and trainer. He is also the host of the weekly firearms podcast Center Mass. He has written over 600 articles for 27 different magazines. He is a reserve police officer and has been training in firearms & close quarter combatives for over three decades. Additionally he has almost 40 years in the martial arts and holds advanced degrees in multiple arts. He currently holds 17 separate law enforcement POST course certifications around the U.S. and is a certifying instructor for law enforcement firearms instructors in handgun, patrol rifle, shotgun and sub machine gun. In addition to training in the US, Mr. Mastison has divisions in Germany, Ireland and Mexico.

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