4 jaw chuck for basic concentric machining and a finger type dial indicator on bore or ideally a snug Gage pin
Rigger, I'm referring to fitting a pin in the chamber or the muzzle end of the barrel, for the purpose of sweeping with an indicator until the barrel is running true to the bore. This insures that features such as threads fit muzzle devices true to the bore and prevent things like baffle strikes, misaligned crowns disturbing flight, and Chambers/leads starting projectiles not true to the bore. It would appear that a 50 or $60 set of gauge pins could be used to fit several calibers in lieu of spending $80 a piece on a caliber specific range rod. I'm not sure where you're going with the pin you are turning in the lathe. I am curious though.