Can anyone explain what’s causing this? This was new Frontier brass loaded with a Sierra #2115 FMJ with 42.5 gr of IMR 4895 powder at an OAL of 2.870”. They were fired in both my 1896/11 and K31. Some cases looked fine, but out of 40 rounds I had about 8 that had these problems. I was also shooting some other reloads with everything the same except with Norma brass and GP11 without any problems. Neither rifle has ever damaged brass like this in the past and headspace is Correct.