.40s ARE tough on frames, plastic or aluminum or steel, doesn't matter. I've seen a lot of .40s go belly up, and heard about a lot more, though I didn't see those.
It's a moderate-sized high pressure cartridge that isn't as well suited to the 9mm frame sizes as S&W would have thought. People tend to forget that the early Grock 40s hammered themselves into wrecks, until they made some mods to the frames.
I don't see the US Army going to .40s anyway, it'll probably be another 9mm of some flavor, or back to the .45.
But, it's all for naught if they don't train the troops better, 50 rounds a year ain't gonna get it.
