I have an H&K USP .40 Compact. I'm trying to get more 12 round mags, and my usual source, CDNN is out, and I can't locate another source. My question is, does the USP .357 SIG Compact mag work for the .40? The case is the same, just necked down, so would it work? Looking at my mag I can't see why it wouldn't, based upon the width and geometry of the feed lips. The only question is whether the front of the mag narrows down to the smaller bullet diameter. Any help would be appreciated.
