I just recently bought a Mosin Nagant 7.56x54 bolt action rifle. Its a cool gun and i would like to use it for deer hunting. I cleaned the barrel, and the inside was FILTHY. After I cleaned all the powder residue out of the barrel I found copper buildup in it. Its not horribly bad, But its visible with a flashlight in the rifling. How can I get this out of there without having to modify the barrel. Can i use a course steal wool to run down through there to loosen the copper up? Or will that mess up the rifling. I know these guns aren't "top of the line" collectors, but I really like the gun and want to use it for a long time. Thanks.