Its bout year old bushy clapse stock 16" barrel, 150gr sst hornidy,and sum 145 monarch steel, stock spring, hydrolic buffer,just put an adjustable gas block havent adjusted the gas yet. also did this before the adj.gas block. Put bout 40 rounds before it started the problem. I polished the chamber and looked at the extracter everything looks normal. I looked at the spent bullet and it has a scar like it tried to grab the case.