I have cold blued 6 shotguns and 5 handguns and there is no question that Oxpho-blue is the best I tried. I read somewhere, maybe Brownells, that cold blue in the barrel is fine and even improves it. By the way, I agree that cold bluing is not as good as hot blue BUT it is extremely easy to fix a mark, scratch etc. The guns I have done always look great because it takes me about 15 minutes to fix any marks.