No pistol round is “best for self-defense;” that distinction must be reserved for rifle rounds. Having said that, I think the available data supports the idea that, for pistols at least, the 9mm round is adequate for self-defense, but not any better than that.

Depending on your expectations, it clearly may not be the “best” pistol round.

The Caliber Story

Some rounds have great stories associated with them. One concerns the popular .45 ACP. The U.S. Army wanted the .45 ACP after having problems fighting the Moro people of the Philippines. The Army’s .38 Long Colt rounds would not stop their suicide attackers so the Army specified .45 caliber for all future pistols.

The .22 Long Rifle round is often said the be the favorite round for assassins. The pistol is compact, can hold lots of rounds, and is easily suppressed. Our CIA and Israel’s Mossad are both thought to use the round in covert operations.

NATO adopted the 9mm round (9x19mm Parabellum) and a huge number of military and police forces around the world, including the U.S. Army, use it. It may well be the most popular round available today.

The Data

But, stories aside, what are the facts and figures associated with self-defense rounds and how do they inform the discussion of “best self-defense round?”

The Hague Convention of 1899, recommendations from which most countries, include the United States, are signatories disallows any expanding ammunition. This is why most of the world’s military use “ball” ammo (Full Metal Jacket). Here we’re considering rounds available to civilians, so only the superior hollow point rounds will be discussed.

Lucky Gunner has done a number of ballistic gel tests using all sorts of ammunition in an attempt to find out how the rounds perform against the FBI standard for their ammunition. The FBI standard strongly influences the choice of police across the country.

Looking at their results, the best of the 9mm rounds (as measured by acceptable FBI penetration and expanded diameter) is the Winchester 147gr Ranger T-Series with an average penetration of 16.5" and an average expanded diameter of 0.74". That should work very well in neutralizing a threat. But are those numbers the best?

Winchester’s 180gr Train and Defend .40 S&W round averages 14.7" of penetration and 0.75" of expanded diameter. Pretty similar and good enough. But Winchester 230gr Ranger T-Series in .45 ACP provides an average penetration of 14.5" and a whopping expanded diameter of 1.0"! If the 9mm is good enough, in these tests the .45 ACP is objectively better.

If the rounds do not expand at all, for whatever reason, the .45 ACP is still going to make a bigger hole, generating more damage, and more bleeding.

There are any number of formal and informal ammunition testing videos on YouTube (knock yourself out). I like Paul Harrell’s work using his “meat target” that simulates human threats with t-shirt material, pork ribs, and fruit. I watched his video comparing different brands of 9mm and .45 ACP and liked it. While the first part is about their velocities, if you watch starting at 7:07, he gets going with the meat target. It’s hard to argue that the 9mm rounds do more damage than .45 ACP.

Other Considerations

Other characteristics of the two rounds influence their effectiveness in self-defense. Important among them is the simple fact that 9mm rounds are smaller and so there can be more of them in a given space. It’s not uncommon for a reasonably sized carry pistol to hold 15, or more, 9mm rounds. That assumes, of course, that you live in a state that allows higher capacity magazines.

9mm’s high velocity can provide better barrier penetration (such as a car’s windshield) while .45 ACP’s low velocity (subsonic) allows for easier suppression. 9mm generally recoils less that .45 ACP so that you can get off more accurate shots faster if your training an practice are not well developed.

Shot placement, capacity, recoil, cost, barrier penetration, and suppression potential all must be considered.

In Summary

So how do you make sense of all that? It depends on the self-defense scenario you want to be prepared for.

For those preparing themselves to face multiple attackers that will not retreat once they see you have a handgun, more rounds may be necessary. If engaging threats behind barricades or in vehicles, better barrier penetration might be valuable.

If you envision only a few attackers or attackers who will not press their attack once confronted, a high capacity magazine might not be important. Barrier (walls) penetration is not usually desirable inside your house.

And, perhaps most important of all, how well trained and how frequently practiced are you? Shot placement trumps all other factors (think of those assassins with their .22 LR) and multiple hits on a threat may be needed to stop a determined attacker.

My personal observation is that nine rounds of .45 ACP (eight in the magazine and one in the chamber) make a formidable defense. Especially so if the user has been trained for self-defense and gets plenty of practice.