After messing about for quite a while, I've got a couple of tips to make them work well. First examine the fit. A couple a mags I have had too much play when seated. Adding a small strip of metal to the front lip catch solved that. Next, quite often the last round or so stovepipes, or the catch to lock open the bolt after the last round misses. Problem is because most of these mags lack a proper follower to prevent the platform in the mag from tilting. The best solution I've found is simple: bend the side lips at the very front of the mag inward. Don't overdo it. 1/8 " will do. They all seem to work great now. Apparently there's a maker in Washington d.c. that makes good quality mags that work consistantly, but I'm in B.C. Bit of a trip.