So, I have been working on the bore of my ar 43 Russian capture rifle for about a week to try and brighten it up. It has very strong rifling but it’s dark and I can see some roughness. It shoots better than my old eyes can hold it, 2-3” at 100 yards off a rest. After 4 treatments with nylon and bronze brushes and Kroil following 24 and 48 hour soaks, I’m still getting thick brown and black out of it. Did the Soviets blue the inside and the outside of the barrels over the corrosion and whatever else was in/on there? Objective is to stabilize any remaining corrosion, and then maintain it. Quit, or keep going? Thanks.