Get some RB-17; it will take that stuff off in about 1 minute. I don't care how bad it is, RB-17 is the best stuff I have ever used to clean a bore, or clean the coon eyes off a revolver cylinder....

Here is a link: Home Page

Good luck!

P.S. it will work equally as well with Hardchrome, blue stainless or any other finish....And it will remove it completely.... That is what sold me on it in the first place, when I saw it demonstrated.