This is a common problem with some mags that can be easily remedied, there is nothing wrong with the basic mags, they just need a little inspection/tweak. Measure the distance between the feed lips, it has to be enough for the lower part of the bolt to enter and push out the round. Measure with vernier calipers, the distance should be at least 0.560 inches. If it is less, say around 0.540 or even less on the 10 rounders I just purchased, the bolt tends to push the round down and give erratic feeding (causing one to perhaps be very disappointed and go buy PMags, which work very well most of the time). Using a Brownells feed lip tool (or a smooth jawed hand clamp, which works even better) gently open up the feed lips (a little at a time on each lip) until the desired distance is obtained. The feed lip spacing on PMags is 0.560 inches. I have several of the Panther Arms mags also and was having some erratic feeding which was remedied by measuring/adjusting the feed lips to 0.565-0.570 inches. They all feed beautifully now and I have no need to throw/store them in the woodshed, lol.