I cleaned for years thinking that my barrel was clean, it shot ok, but in essence I was just taking the top layer of fouling off. I shoot good barrels, break them in right (IMO), and don’t get visual copper when cleaning until the barrel is getting up there in age.
I pulled a 223 match barrel off and replaced it with a 223AI, it had about 1400 rounds down it and had been “cleaned” as I have done in the past. So with nothing to do one day, I was checking my small barrel inventory, and came across that 223 barrel. I scoped it and could not believe what was in it. The lands and groves were covered with fouling, it looked like a mountain range. I started cleaning it, Butches on a patch came out white! How could that be I could see black streaks in the groves like they were painted on. Hitting it with a bronze brush I slowly got results. The baked on carbon in the groves took JB and a lot of elbow grease.
Now the barrel is really clean, does it need to be this way to shoot? Maybe yes, maybe no. For all those who say, my barrel cleans up with four patches, good for you, I have never seen one. My regime now is to clean and get all the carbon out along with fouling and of course copper if it shows. My rifles shoot great, score well and are consistent match to match. I do send 10 rounds down before a match, is that necessary? I’ve always done it, so I may be just superstitious before a match.
BTW, my round counts are at or beyond anticipated barrel life, cleaning doesn’t seem to affect that issue.