So, as I've posted, I'm building a John Armstrong rifle in .54 caliber. I purchased a new Green Mountain barrel for that project. I polish the bores of all of my rifles including the unmentionables. I started doing that when I began casting and shooting cast bullets. Yes, it makes a difference! I use Turtle Wax chrome polish on cleaning patches. About 100 strokes. So this morning I was in want of something to do so I decided to polish the bore of my new .54 cal Grn. Mtn. Barrel. This is what came out of it! See attached pics. I waded through it and now the bore is clean, shiny and smooth as a baby's bottom!