memilanuk
Gold $$ Contributor
@ckaberna I have had the *exact* same thing going on in my last three barrels - two Bartleins and one Krieger. I have tried bronze brushes, patches and felts with abrasives, and various chemicals (all the ones mentioned so far plus many more). Nothing touches that crap in the bottom of the grooves so far. Just because the patches show clean doesn't mean anything - it still looks like that when I run a bore-scope in.
In my barrels it started forming a few inches ahead of the throat, and just kept growing towards the muzzle as the round count increased. .308 Win pushing 200 Hybrids and/or 200.20Xs with Varget or H4895.
In my barrels it started forming a few inches ahead of the throat, and just kept growing towards the muzzle as the round count increased. .308 Win pushing 200 Hybrids and/or 200.20Xs with Varget or H4895.