One of the cliches of concealed carry is trading in that compact 9mm for a bigger gun for winter, and one form of that cliche is to switch to a big ‘ol .45, typically some sort of large .45 ACP semi-auto pistol rather than, say, a big gun in .45 Colt.

To the town of Agua Frio rode a strang…never mind.

Anyway, winter and the extra layers tend to bring out those big old Glock 21s, HK USPs, S&W M&P45s or perhaps even a 1911 since they’re that much more concealable.

One of the tenets of what could otherwise be called Fudd lore is that .45 ACP is needed to penetrate through the additional layers of clothing. While most people have accepted that any decent quality 9mm bullet will have no issues, some folks cling to this idea.

If you’ve ever heard this, or believe it, we’re about to throw some water on the idea.

Not, of course, that you shouldn’t carry a .45 if you want to, or get more use out of a gun that mostly lives in the safe if you want to. If you want to, go ahead. Instead, the idea is to address what .45 ACP actually does vs what people think that it does.

Let us begin by acknowledging the following:

.45 ACP has common projectile weights of 185, 200 and 230 grains. There are lighter and heavier, but those are common.

For standard pressure loadings, typical velocity and muzzle energy is roughly 1000 fps on the lighter side to about 800 on the heavy side, with about 350 to 400 ft-lbs of muzzle energy.

There are some hotter standard pressure loads, but they’re rather rare.

Granted, .45 ACP 230-gr hardball does make a decent poor man’s woods pistol. It’s also the case that .45 ACP is certainly underpowered given its case capacity; .45 ACP +P loads are a different animal as the velocity and energy are in the same company as .357 Magnum.

However, the standard-pressure loadings just aren’t that much to write home about.

While obviously slower than standard-pressure 9mm, garden variety 9mm Parabellum (115-, 124- or 147-grain) travels at about 1150 to 1000 fps in standard pressure loadings, producing around 350 to 370 ft-lbs of energy in most standard pressure loadings.

In other words, .45 ACP nets no gain in velocity, and a typical advantage in muzzle energy – again, for most standard pressure loads; you can, no doubt, find exceptions – of around 10 percent.

That modest gain comes at a cost, namely double the recoil energy. Per Chuck Hawks’ handgun recoil table, a 2-lb pistol firing 115-gr 9mm at 1150 fps produces about 3.8 ft-lbs of recoil energy, but a 2.25-lb pistol firing a 230-gr .45 ACP projectile at 850 fps produces 7.9 ft-lbs. Which, as it happens, is exactly why the FBI switched to 9mm several years ago, per their memo that was posted by SOFREP. Agents fired faster and more accurately with the smaller caliber.

But does that extra grain weight and modest gain in energy actually translate to better wounding or performance in testing?

In the 1980s, it did.

The FBI selected 10mm as its duty round, but noted that .45 ACP had better performance in their laboratory testing than 9mm, though not as good as 10mm and, per the report by the FBI’s chief ballistician John Hall in the FBI’s news bulletin in 1989, with slightly less accuracy.

The cup and core hollow points of the era performed well or at least well-enough in the FBI’s ammo test in .45 ACP, but less so in 9mm; however this has completely changed with modern ammunition.

In comparing modern 9mm hollow points alongside modern .45 ACP hollow points, per Lucky Gunner Labs – who use part of the FBI’s protocol, though without barrier tests – .45 ACP barely perform any better in gel tests.

Expansion, when it occurs, is typically more dramatic, but .45 ACP also has a greater propensity to clog on clothing, preventing expansion. Various 9mm loads in their testing also fell short, but the underperfoming examples tended to fall short of the 12 to 18 inches of gel penetration.

Most that did were gimmick ammunition (typically lighter/faster or non-typical projectiles) but most modern JHPs satisfied the base criteria of 12 to 18 inches of penetration and some expansion.

Of course, at some point the discussion of wounding may come up. Air in, blood out as the saying goes, but the reality is that any advantage there is academic; no real link between faster incapacitation and handgun calibers has been realized to date other than noting that some bad guys went down quicker when shot with a particular caliber/load than others.

That would roughly be the supposed Strasbourg goat tests – which were never confirmed to have actually happened – as well as the Marshall and Sandow studies which – while worthwhile to read – also fall short in explaining why things happen as opposed to just cataloging what did.

The point here?

As far as anyone can tell, there’s no real advantage to .45 ACP as a winter carry round compared to a 9mm loaded with modern (meaning bonded) hollow points. So no, there isn’t any need to.

But there’s no reason not to switch if you want to switch. The .45 ACP is a proven fighting cartridge, just not the cannon some people pretend it is.

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Sam Hoober is a Contributing Editor to AlienGearHolsters.com, a subsidiary of Hayden, ID, based Tedder Industries, where he writes about gun accessories, gun safety, open and concealed carry tips. Click here to visit aliengearholsters.com.