relliot, I measure them, I am fanatical and meticulous when it comes to keeping things in order. I am wondering if maybe I should polish the lips, I get exactly what you are saying, it might be the release point where the round begins to flip up. There doesn't appear to be any burrs, but the edges are sharp- these 10 round CZ mags sheetmetal is pretty light and there isn't much of a "landing" on the edges. I will go over each and every one of them and pay more attention if it might be a particular mag that is giving me trouble. As far as the slidestop, I do have the new one, and an original that is cut the same way as the new ones. Gotta get packed up, match this morning in Gagetown!