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Best Defensive Ammo: 9mm vs. .40 S&W vs. .45 ACP

The debate on which is the best defensive pistol caliber continues.

Best Defensive Ammo: 9mm vs. .40 S&W vs. .45 ACP

Best Defensive Ammo: 9mm vs. .40 S&W vs. .45 ACP (Handguns photo)

When most shooters talk about “serious” defensive pistol calibers, the conversation usually bypasses the .32 and .380 ACP and centers around the 9mm Luger, .40 S&W and .45 ACP. And the general areas of contention usually revolve around controllability, capacity and power.

The much-used term “stopping power” has been bandied about by handgunners since, it seems, the dawn of time. But the actual physics involved aren’t as disparate as they might seem, despite the passionate arguments from one side or the other.

Black Hills 125-grain HoneyBadger
Black Hills 125-grain all-copper Honeybadger offering with its fluted bullet configuration. (Handguns photo)

Speaking metrically, these three auto standbys are 9.01mm, 10.2mm and 11.43mm, respectively. Objectively speaking, that’s really not all the great of a bullet diameter span, but it’s been more than enough to fuel countless hot-stove arguments for decades.

The velocity span, naturally, is a bit larger. A .45 ACP 230-grain hardball load has a muzzle velocity while higher-pressure 9mm Luger rounds can be around 1,300 fps. Of course, the 9mm and .45 ACP have a considerable longevity advantage over the .40 S&W. The .40 was developed in 1990, while the 9mm was designed in 1901; the .45 ACP in 1904.


Hornady Buffalo Bore .45 ACP
High-performance .45 ACP loads run the gamut between 200-grain +P JHPs to 255-grain HCs. (Handguns photo)

The .40 S&W was developed for the FBI as a replacement for the “10mm Lite” loads that came into being as an easier shooting alternative to the full-house 10mm auto—which, at least in its early 170-grain Norma loading, was, well. . . stout. The .40’s main selling point was that it had an overall length of 1.135 inches, which permitted its use in 9mm-size platforms—something the .45 ACP (overall length of 1.275) could not.


Unfortunately, the .40 S&W—despite much initial fanfare—took a serious hit in popularity few years back with the resurgence/re-adoption of the 9mm among a whole lot of state, federal and local law enforcement agencies.

It was felt that improvements in bullet technology boosted the 9mm beyond what the round achieved in the decades since it was a law-enforcement standard in this country. Controllability is also a factor, since the .40 S&W—in 180-, 165- or 155-grain configuration—was a lot closer, recoil-wise to the .45 ACP—particularly when it was housed in a relatively short, light pistol.

Federal .40 S&W
The .40 S&W has been popular with law enforcement for some time, but it's quickly getting nudged out by modern 9mm cartridges. (Handguns photo)

The 9mm holds a capacity advantage in double-stack magazines as well. This is illustrated in three similar-size models in the Smith & Wesson M&P lineup. In the full-size frame, the 9mm version is 17+1 whereas the .40 is 15+1 and the .45 ACP is 10+1.

Economically speaking, in normal times, bulk-pack 9mm FMJ practice ammo is less expensive than .40 or .45, although I’ve seen .40 ammo in places that were tapped out of 9mm and .45 ACP. And, of course, the old days of running across large quantities of “practice grade” 230-grain GI hardball are now pretty much a fantasy.




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