A gun chambered specifically for brass cases will have a larger bore than one chambered for paper. If the chamber itself was cut with the same reamer having the same angle to the cone this would result in a shorter length to the cone. If the gun has a nominal bore dia of .729 or close then the short cones would only show it was cut with a reamer having a steeper angle to the cone, & still intended for paper shells. A subsequent "Back Boring" would of course produce the same results as an original boring for brass.
