Robert;
To actually polish out a chamber, finish rubbing compound , which is a very fine abrasive, would be the compound of choice.
I have 2.5x20 Simmons shotgun scopes on some of mine , the longer eye relief, 5 to 9" allows me to mount the scope far enough forward that no hammer spur is needed.
Lee RGB die set is about $14 from MidwayUSA
Don