I was priming some Hornady .300 Blackout cases when I noticed some cases just wouldn't accept a primer. I forced one in, but it was ruined in the process. I noticed that all the brass marked as ".300 BLK" was this way, but not the brass marked ".300 Whisper." I ran the stubborn cases through the swager and now, no trouble seating primers. I was surprised; I didn't expect commercial brass to have crimped primers. Anyone else encounter this with this or another caliber or brand of cases?

Ed