Quote History Quoted:
How does HK to only manage to fit 15 rounds of 9mm in such a large pistol?
Glock/M&P = 17 rounds
Caracal = 18 rounds
XDm = 19 rounds
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I was looking at my P30 mags wondering the same thing, and I think I know why. On the sides of the magazine there are trenches that run from the top to the bottom of the magazine. They're pretty deep, and probably reduce capacity a bit. I couldn't believe that HK would make a wide magazine and have 2 capacity reducing trenches on both sides. Then I realized that those trenches probably make the magazines feed much, much easier, as the rounds in it are contacting just those small trenches instead of the whole side of the magazine. That's gotta reduce friction quite a bit. On top of that, any debris that gets down in there will be less detrimental. Also, at the top of the magazine, there is the taper. Every magazine tapers down at the top to reduce the double stack to a single stack, but it seems like the HK mag's taper stretches a longer distance, but I'm not sure, and I don't want to dig another mag out of the safe to check. But if so, the longer taper distance should make forcing the double stack of rounds into a single stack much eaiser as it's done over a longer distance with a shallower angle, thus further reducing friction.
These two features will probably extend the life of the magazines, because as the springs weaken, they'll still be able to perform their function with all the reduced friction. I'd gladly reduce capacity by 2 or 3 rounds if those things are true, and if the sacrifice will ensure more reliability and longevity.
I'm pulling all that out of my ass, so that may all be bullshit, but until someone comes along and tells me differently, I'm going to assume those things are true. Doing so alleviates the disappointment I feel when I see Glock 17rnd mags are the same size as my P30 15rnd ones.