.45 ACP Versus 9mm Parabellum

17 May

Which caliber is a better self-defense round? Is the 9mm adequate for defense? Shooters, police, and military have debated these questions for decades. There’s really little to say but this: Pick which one you like and go with it. Select a good JHP bullet. Practice until you shoot moderately well.

Years ago, Jeff Cooper promoted the .45 ACP as the greatest pistol defense caliber around. Cooper followers scoffed at the 9mm. They even scoffed at the 125 grain JHP bullet in 357 magnums. The 125 grain JHP in a 357 magnum is a proven manstopper.

To measure “stopping power” the Cooper school developed the concept of “power factor” which is really nothing but momentum, mass times velocity. Momentum alone isn’t the best predictor of pistol stopping power. A smaller lighter, but much faster, bullet can have less momentum and still transfer much more energy to the target. It can damage more tissue.

Decades ago, expansion of pistol bullets was hit or miss. You’d settle for a clean 45 caliber or 38 caliber hole. The best defensive loads today actually do expand, leaving the final pistol bullet about 1/2 an inch to as much as .7 of an inch in size across. That’s a nasty wound, no matter what caliber it came from.

Most pistol bullets don’t actually have “stopping power.” When people die from pistol gunshot wounds, it’s usually because they bleed to death. When shot, many people wonder around until blood loss makes them dizzy and they sit down. The only surefire way for a pistol shot to reliably stop somebody is for the shot to disrupt the central nervous system, which means it penetrates deeply into the brain or the spinal column. Other than that, a single pistol shot might or might not stop an attacker.

Given that damage to the central nervous system or massive blood loss is what makes a shot most effective, it should be clear that bullet placement is paramount. Imagine a line from between the attacker’s eyes down to the center of the solar plexus. The closer shots are to this line on the upper chest, the more likely the attacker will be stopped. More peripheral shots are usually less effective.

Because there is no magic bullet, defensive shooting schools often teach to keep shooting until the attacker drops. While full power 357 magnums are very effective, they have a major weakness: the recoil is so great that it interferes with the ability to get off fast multiple shots. This is why many load their 357 magnum revolvers with 38 special +P ammo. Fans of the 9mm will list this as one of the advantages of a 9mm: They’ll be able to get off more shots rapidly than they could with a .45 ACP. But as countless shooters demonstrate, accurate and fast shooting can be done with a .45 ACP too.

At the end of the day, choose which caliber you like best. And, if you don’t like either, there are many other great calibers to choose from!

Charlie Palmer -author, The Prepper Next Door: A Practical Guide For Disaster And Emergency Planning (link to book on Amazon)

For those who want to read more about “stopping power,” from a technical standpoint, the best discussion I’ve found online:



Many shooters would love a semi-auto equivalent to the .357 magnum. The 38 Super had the potential to be great, but is rare. Even rarer is the 9×23 Winchester. It was developed as a “magnum” version of the 9×19 mm Parabellum or as an improved version of the 38 Super. 9×19 means a 9mm bullet diameter and a case length of 19mm. The 9×23 is 4mm longer and is reported to shoot 125 grain bullets up to 1,500 feet per second. Shooters with 1911 pistols in 38 Super can purchase 9×23 barrels. Another contender is the 357 SIG which is touted by ferfal in his book, The Modern Survival Manual, which is a great read, by the way. To me, the .357 SIG just looks wrong!

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