It sounds like that the case lip may be too crimped. If my memory serves me correctly, all autos head space on case lip. It is real ease to put too much crimp. I did one time and results on 45s was no boom. I was experimenting on fatigued brass that would not firmly hold 230 FMJs. The bullet actually went too deep into chamber. Not enough force back against firing pin. Manually drop on in stack and mark it. Just a suggestion!