I have lowers from four different brands (BCM, PSA, Sionics, and Spikes) and all will take and drop gen M2 and M3 Pmags just fine. When I bought my BCM there was a lot of drama at the time about whether their lowers would readily take gen M3 mags. With the others I just got lucky I guess. When I bought that lower I was working at a shop that carried BCM so I made sure to get one that dropped them freely. I recall when this issue first came to light BCM took the stance that their lowers are designed specifically to take mil-spec mags and that anything else is basically a crap shoot. However, that was before the gen M3 Pmag became the de facto military magazine. I guess BCM hasn't changed their position.