I've seen people ask why it's a bad idea to use A-MERC brass for reloading. I went through a batch of range brass a while back and found these. There were more A-MERC cases, all had some deformation at this area. In case some might be inclined to blame the gun, check the primers, these were fired from two different guns. The one on the right is unmistakably a Glock, the other is not.