There's a piece missing from most of the responses. I haven't heard anyone say "that won't come out". If it won't come out, then I agree: "it's a working gun, just live with it". But I too, like to keep things in good condition, at least as good as they can be. So, if there's an opportunity to fix it, I say give it a try. I think Walt's post above is on the right track. LIGHTLY rub with a ScotchBrite (maybe with some Hoppes or gun cleaner). Be very careful about shining up the "damage".