When I did .308 and 30-06 chambers I would use a pull through reamer. This was a standard for many years.
I never found that measuring factory datum points were accurate.
Failure is part of success!
This year will go down in history. For the first time, a civilized nation has full gun registration. Our streets will be safer, our police more efficient, and the world will follow our lead into the future!" -Adolf Hitler,1935"