Heard of a new trick to clean up nasty old bores - rusty etc. - Take the barrel, trigger etc. off the stock and get a pvc pipe big enough to slide it into. Cap off one end and put the barrel and whatever else you are trying to clean in it and fill it up with brake fluid - let it set for 24 hours - amazing how it cleans it up - won't hurt it either. Heard this from a local gun dealer cleaning old mausers.