I'm not sure that I am in the correct forum, someone please correct me if I'm not. I am loading some Missouri cast and coated bullets (subsonic loads) for my cz 527 in 300 Blackout. Load has been really promising shooting about moa at 50 yarks. Picked up my brass and noticed an unusual sort of thing. Right at the top of the little rounded shoulder I have about 3 cases show a very short lenier crack in the brass. If anyone has had this problem please let me know! This is blackout brass that was formed from 221 fireball brass. But I noticed a few Federal factory brass showing the same thing.