Squib308 reported: agree seems like an ammo difficulty. Probably the brass is bulging? Have you ever inspected the winchester brass just before vs. immediately after firing? I truly feel like being slide mounted with a centerfire pistol is about as severe since it receives, and just about anything that survives https://highimpactrounds.com/product/mossberg-590a1-spx-12-ga-20in-8rd/