Thanks to all who replied, all possible problems. Solution, Eric and others solved problem. Slide stop was ground from builder, mag followers were not (grams). After 20+ k rounds things loosen up enough where the bullets (same for all 20k rounds), were in fact occasionally hitting slide stop. Ground back of slide stop as much as I dare. No problems with 140 rounds fired. Will do more. Also going to grind the corner of the grams followers down to make sure this never happens again, particularly since it is my match gun. Again thanks to all, you guys are a big help!