I have a friend that works down the street a machine shop. They have great measuring tools there. He will mic a few for me. As well as a pure lead round ball that I used to slug the barrel with today. I checked the caliper against 10 Laser Cast 350 grain sized at .459 all of those were .459 on my caliper.
Oh and for the micro grove rifling. I am looking down the barrel, and the rifling does not look shallow at all. It is deeper than most of my hand guns, and several of my good shooting rifles.
No matter how many times you do it and nothing happens it only takes something going wrong one time to kill you.