1. It isn’t 10mm.
Let’s start with the harsh reality. The 10mm may be the perfect self defense round. It makes a hell of an impression. The 10mm slugs weigh the same as .40 slugs, but are moving a whole lot faster. Yes they produce nasty recoil. The recoil is punishing. Follow up shots are not as fast as they would be with a lighter load (like a 9mm), but I’m still inclined to say bigger is better. And the 10mm has more than enough stopping power for anything on this continent. Two legged or four legged, a well placed 10mm will dispatch a threat.
The .40 was designed as a compromise. It is bigger than a 9mm, but smaller than a .45 ACP. It feels like a round that was designed by committee. I can see the meeting clearly in my head. No one agrees on what they want. They know it isn’t the 9mm, and they know it can’t be the 10mm. So they take 9mm ballistic performance expectations and then dumb down the 10mm until it meets those expectations. That allows them to do something I consider really dubious, which will be discussed in #2.
2. Most .40 caliber guns are just retrofitted 9mms.
Fundamentally. Some, like the GLOCK 19 and 23 are built on identical platforms. But there is an increase in recoil. Shoot a GLOCK 19 side by side with an identical GLOCK 23 and you’ll see what I mean. The 19 is flat shooting and damn fast. The 23 produces some serious muzzle flip. This isn’t a big deal if you aren’t shooting much, but it can wear you down after a long day of training. I took a 23 to a handgun class a year ago and went back home and immediately traded the 23 for a 19. I’ve put 500 rounds through the 19 in an afternoon with almost no hand fatigue at all.
The 10mm doesn’t hurt as badly as the .40. I think this is because the 10mm guns, like the GLOCK 20 are much more substantial. The weight helps with the recoil. It still produces enough shock to wear on your hand and wrist, but I haven’t had as much of a problem with it.
3. The .40 can be dangerous.
Compromise almost always sucks. No one gets what they really want. Because the case has been shortened, there is less room for error. Get on the interwebs and start reading up on .40 S&W failures. If you happen to jam the nose of a bullet into something unexpectedly, like can happen during a miss-feed, you may push the whole bullet into the case. Even a fraction of an inch can result in disaster. It will still chamber, but the pressure builds too quickly. In unsupported chambers, you’ll get massive case ruptures–or catastrophic failures.
4. Limited ammo supply.
The .40 S&W seems to be regarded as a carry round. As such, there are fewer good training rounds available. During the big ammo shortage we went through last year, .40 was the only round on the shelf. Winchester, mostly. That was a big plus in .40’s favor. But I want to be able to pop into a big-box store and pick up 500 rounds of ammo and a gallon of milk. And that gets expensive with .40. The selection of carry ammo is good, better now that SIG is making their own. I’ve been working my way through a case of it and I have no complaints that aren’t purely philosophical–but it would sure be nice if I could get identical training ammo. I know it is possible, but it isn’t likely.
5. Limited capacity for limited gains.
My last complaint my be a bit hypocritical, considering I’m such a fan of the 10mm and the .45 ACP. Okay. I’m fickle. I just just can’t help thinking about capacity. Call me old fashioned, but I still think it matters. If I’m going to carry an automatic in bear or moose country, it will be a GLOCK 20. If I’m not in danger of getting mauled by a brown bear, I’m going to carry a 9mm. There is so much selection, and capacity is about as good as it gets.
The 9mm GLOCK 19 I mentioned earlier has a capacity of 15+1. The 23 is 13+1. I know that I’m splitting hairs there, but I’d prefer to have the extra rounds. The 10mm GLOCK 20 and the larger framed GLOCK 22 (.40 S&W) both have 15+1 capacities. Why wouldn’t I want the 10mm? Why would I want to compromise? I’m not ordering a medium shake to go with my medium fries today at lunch. And, if I have a choice, I’m not riding the .40 Short Bus.
As always, I turn to the empirical data. Ballistics by the Inch does amazing work with ammo testing. And they have a nice section for each caliber where they run production model guns and record their findings. Take a look at the two charts below. The .40 bullets are heavier–that’s a benefit. And they’re moving pretty fast. Yet, as physics dictates, the heavier rounds are moving more slowly.
Yet the 9mm is no slouch. I still believe the the bad reputation of the 9mm is due to the dubious performance of 115 grain ball ammo in combat. The increase in capacity, though, and the speed that comes from greater control still make the 9mm, at least for me, the winner.