Bill you are completely correct on a clean bore is a must and I'd also be in agreement in the use of Aluminum Oxide and Kroil if I had a bore that had corrosive particulate trapped under some copper fouling. My point is, I wouldn't use this abrasive mix every time I cleaned my bore. In fact on a "new" barrel you will get the copper to fill in the microscopic fissures, which is "burnishing" a new barrel, but that's a whole other topic all together, and is off this topic.