Most of my ex-mils never clean up completely as far as carbon is concerned - patches always come out grey at best. They still shoot okay, and a couple of the bores are pitted and dark. A damaged/worn muzzle will destroy accuracy, maybe yours has this issue? If so, counterboring will help, or even chopping a bit off the end. I had a Columbian Mauser with a worn muzzle that missed the target at 50 yards, or those projectiles that hit were completely sideways. I chopped off 3/16" (hacksaw) and hand filed a flat crown - shoots as good as my other Mausers now.
