I know most will have a heart attack about this but... try a stainless steel bore brush if its bothering you that bad. Get some Boretech Eliminator, its a surfectant and will lift carbon, copper....
Stainless brushes are softer then barrel steel and won't hurt them, let the barrel soak for about 15 mins, scrub and then patch it out.
clutches left arm...
ignore my complete lack of capitalization. I still have no problem correcting your grammar.
I never said half the stuff people said I did-Albert Einstein
You can't believe everything you read on the internet-Benjamin Franklin