I have tried some of the more popular cleaning liquids and have concluded that none of them clean all, or very much, of the residue out of your barrel without using a brass brush. Iosso, Butches, Hoppes, Boretech Eliminator - they all leave copper and some carbon in your barrel, even after applying them and letting them sit for 15 minutes or longer. A good bore brush and persistent scrubbing will remove the copper. But a pass or two with the brush, even after letting the cleaner sit for a while, will not remove all of the residue. You can see this with a borescope if you bother to look. Some of the carbon residue down the barrel (not just at the throat) is harder than the powder residue that comes out easily after you fire a few rounds. The patch will come back clean, but if you let the barrel soak for a while in your favorite cleaner after getting a clean patch, the next patch you run through will have significant carbon residue on it. This is my experience after testing on two barrels for the last week or so. I have concluded that clean barrel is absolutely a subjective term that we use to notate when our barrel is clean enough to group good. In reality, the barrel may not be clean at all, i.e. copper free and carbon free. And, I am in search of the best brushes to use as I feel that they are a must. Have I missed something?