Mossberg Patriot over-bored chamber?

[SHELL SHUCKER]

That's the thing. It's not just one loading. Every round, irrespective of brass, bullet weight or style, or powder, exhibits the fouling. I usually load maybe a grain below max according to my Lyman manual so nothing too hot but nothing too anemic either. I plan to load some 150 gr. and 165 gr. with max loads (different powders and brass) when the ranges reopen and spend a day trying out different recipes.

What dies are ye using? Are you using mil brass or commercial & and are you full length resizing each time?

I've had no worries with the .308 sooting up with my light or hefty loads by using fresh commercial brass and full length sizing it for the first shots. After that, the next reloading was done using only a Lee collet neck sizing die. I finish the process using a Lee factory crimp die.