Was loading .45ACP on the Dillon 550 yesterday. I had completed about 130 rounds when a primer went off when seating. After checking to be sure I hadn't embarrassed myself, I checked the case in station 1. I expected to find 2 primers, one in the case and one in the primer cup. There was only the primer(fired) in the casing. The primers I was using were Wolf large pistol. I'm trying to get rid of all Wolf primers. I've had too many problems with Wolf small pistol primers and won't use them at all. Up to now I haven't had any problems with large primers.
I can't figure out what I did that might have caused the primer to go off. Has anyone else had this happen? I'm not trying to find an excuse, just what may have happened so it doesn't happen again.