OK I've gotten some shooting in today after getting a splinter out of my 6 year olds hand "she always asks if it'll hurt" but I did get some shooting in.
Since I didn't have the time to grab my meaures & gear to do a good bench shoot I thought to grab the first tray of preloads that I had, my rig & my 11" X 9" X 11" box of used magazines with a traget face attached "great for keeping your Lead."
Conciddering that at 20 yards I was lucky to hit this box much less have a decent amount of shots on the target before shooting one handed & especially with a 35gr. charge of FFFG Goex I figure that 15 out of 17 shots was pretty darned good, the ones circled in magic marker is the first 5 shots.
From what I've gotten is that the Chamber diameter should be .0010 - .0020 larger than the Grove diameter of the revolver.