I'm just starting a stub job converting a 12 ga H&R to a 458 smokeless Muzzle loader. I needed to mount the chamber end of the barrel in a chambering fixture and machine it to exact length.(3.0") Then I would need to bore it out leaving a shoulder .560" from the end buried in the chambering fixture. Th last step would be to singlepoint a 1 x 16 thread to the shoulder to accept the barrel stub. My problem is to do this in one setup. A made a simple gauge that will allow me measure both the length of the tube and the location of the shoulder with limited access to only one end. There's probably a Roger Ramjet official tool that already does this but I don't know what it is.