Looks like you have stumbled on to the way the big gunmakers have managed to keep their costs down, by eliminating all hand work, polishing and fitting. It takes a skilled craftsman to do this right, and that kind of labor does not come cheap. You are dead right about polished steel being more rust resistant, this applies to normal gun steels just as well as stainless. You can have it polished, but then it might be too shiney to hunt with. There are also some other ways to finish the metal besides paint. Dura-coat comes to mind, and there are various baked on finishes usefull for stainless.