FWIW, I would perform one of the thorough, overnight cleaning methods described by other posters, and then never worry about getting it "clean" again.
The bores in these old rifles are just too rough even when they are in good shape to ever come out clean. Clean it as thoroughly as you can, then fire 50 rounds of old milsurp ammo through it and clean it again. You'll think you're starting over from square one again!
44henry
