Update.
I've finished chambering the barrel in question. I think it turned out very nicely. The bronze wedding ring worked, but the screws still flattened the radius I put on it which would affect the barrel's ability to pivot, so I think I'll try steel the next time. The reamer cut on size at the base (a .471 pin would just start) and chamber is round with no runout or chatter. I nearly screwed the pooch when I bumped the cross slide handle between cuts on the cone, it's supposed to stay put and carriage controls depth. The next cut started MUCH deeper than expected but I had far enough to go that it cleaned up. Torqued the barrel to 40 lb-ft. I ended up with .008" bolt nose clearance and the stripped bolt drops on the GO gauge but will not close with a .002" shim on the back, so I'm happy. Crowned at eleven degrees with a light 45 degree kiss on the inner radius. Made a brass driver pilot for the muzzle, padded with two cleaning patches and then spun it for a while at 400 rpm while I ran a green Scotchbrite pad on it. Hope to see how it shoots this weekend. I appreciate the wise counsel that was shared.
Greg