Q A good friend and I work together to do a fair amount of hobby gunsmithing. He has a lathe and together we have chambered and fitted a number of barrels. We are currently engaged in a friendly dispute over polishing chambers. He thinks you should do this after reaming, while I read somewhere years ago that you should not do this. The idea as I remember was that a highly polished chamber wall would not allow the brass to stick properly when it expanded as the cartridge was fired. What is your take on this issue?
A Like so many issues in this world, it all depends on how far you go. Normally, I will just touch the chamber a bit with abrasive to smooth out any roughness left by the cutting action of the reamer. Keep in mind if a reamer is used properly with adequate lubrication, the newly cut chamber should be very darn smooth. In one sense, my polishing is more cosmetic than anything else. Also, the chamber after polishing is a long way from having a mirror like finish. That, in my opinion is far too much polishing.
While I have never run across any current research or work related to polishing chambers, I do remember reading about some work done back in the 1920s at the U. S. government facility at Springfield Armory. Remember this was during the time when the 1903 Springfield rifle was in use and there was some question as to whether or not a highly polished chamber would make extraction of the fired cartridge case faster and easier. This was certainly a legitimate concern when you had a bolt-action military rifle. In any event, after the research and test work was done, it was found that a highly polished chamber had no significant effect or easing of extraction. So as far as I'm concerned, polishing a chamber is not really all that significant or important for anything other than cosmetics.