yep thanks fer the replys guys , but i really think it is machining marks it looks like a lathe cut that resembles a screw affect ,but its jagged ,at least a in or more , i took a look at my old knight that dose have damage down there , and it is not powder crude , my ? is should i just jb that area , or the hole barrel ? its still a good shooter ,and if i dont have to mess with the muzzle end i would rather knot , opinion please