Squib308 stated: concur looks like an ammo concern. Probably the brass is bulging? Have you ever inspected the winchester brass just before vs. immediately after firing? MGL Chapter 140 claimed: “Huge potential weapon”, any firearm, rifle or shotgun: (i) that is certainly semiautomatic with a set substantial potential feeding system; https://highimpactrounds.com/product/mossberg-590a1-spx-12-ga-20in-8rd/