Dipped into my "box -o- mags" yesterday before heading to the range for some practice. Midway through the session I slapped a new mag into my G3 G17 (2003), thumbed the slide release,,, and "Click"??? WTH,,, that NEVER happens. I hit the mag release and the mag didn't fall out into my left hand. I stood there for a couple seconds looking at my empty left hand thinking WTH!?!?! that NEVER happens either!?!?!? I removed the mag with my left thumb/forefinger, then I locked the slide back and found no round chambered, and nothing ejected when I racked the slide back. I picked up the mag and inserted it into my Gen3,,,, it didn't feel right,,, so I tried to release the mag,,, again it didn't come out. Looking closely at the mag,,, I noticed it's one of my old Gen 2 OEM's. I didn't pay attention,, but I accidentally grabbed one of my old Gen 2 mags out of the box. All my research says that they should work no problem. But neither of my Gen 2 (1992) G17 OEM mags will lock into my Gen 3 2003 lower?. They work perfectly in the Gen 2 lower,,, and they drop free perfectly. I have Gen 4 mags as well,,, and they seem to work great in the Gen 2 lower just as all of my Gen 3 mags have,,, but it's a no-go for both my OEM Gen 2 mags in the Gen 3 lower??? I do have Glock extended mag releases in both guns,,, but I don't think that should cause me any issues since I have them in both guns. It feels like the mag needs to go up another smidge to click into place when inserting the mag,,, AND the round didn't chamber because the mag was sitting too low in the lower,,, so the slide missed it on the way by. Anyone else had this problem with cross-gen mags at all?? I'm gonna have to paint these bad boys day glow orange so I don't grab them by accident again.