Squib308 mentioned: concur sounds like an ammo situation. Probably the brass is bulging? have you inspected the winchester brass ahead of vs. just after firing? I did deliver an email and got a reply past night. They say they're sending a completely new component proper out. I'm rather delighted with https://highimpactrounds.com/product/mossberg-590a1-tactical-12-ga-20in-8rd/