dpms 7.62x39 upper..feeding problems

This is a just F.Y.I..I have a dpms upper 7.62x39, and the USA mags wouldnt feed, I had jam after jam after jam. I took off 1/32 off of the top of the locking lug on the mag, and they feed flawlessly. Apparently USA bored the square hole, just a little too low, so it rubs on the carrier.,SITS TOO HIGH, inside the upper. I guess you get what you pay for...Just in case you guys are having trouble as well.