[Wolvee]

I have hunted high and low to no avail, the best I have found is Promag 20rd for the USP. My question is will a USP mag work in a HK45 or am I S.O.L. And dreaming of high capacity?

Instead of dreaming and wishing you should know, you reload when you have time, not when you run out so mag capacity really shouldn't matter.