This with some 100% Copper "Chore Boy" wrapped around your caliber (bore) specific mop. The chore boy increases the diameter somewhat. It does not take much. It is a learning curve. Scrubs very well. It has sharp edges. Good for the barrel also.
Kroil seems to get under everything. I think I remember reading it can permeate to one millionth of an inch. Between the cells in your skin even.
I never use stainless brushes. Too hard.
