A clean patch is NOT an indicator that the barrel is clean. Only loose stuff comes out on a patch. Hardened carbon and copper both will yield a clean patch once the loose stuff has been scrubbed out of the barrel by prior patches. The trick is to get all that junk in the barrel loosened up. Good copper solvents will loosen the copper, but my experience agrees with that of the guys who say that the baked on, hardened carbon cannot be dissolved by any known agent. It takes physical intervention to get that stuff out.
It was only after I got a borescope that I realized this. That does NOT mean you can't get a barrel clean without a borescope. It just means you can't tell for sure if it's clean or not without one, and clean patches certainly won't tell you.
It was only after I got a borescope that I realized this. That does NOT mean you can't get a barrel clean without a borescope. It just means you can't tell for sure if it's clean or not without one, and clean patches certainly won't tell you.