the only way to get matching chambers is to have a smith make them with the same reamer from barrel blanks…
This ^^^
Even then, one may not always be able interchange fired brass. For example, the case head protrusion from the barrel breach of my push feed model 70 is slightly less that the protrusion from my 40X Remington, by design. This results in expansion further forward on the case web area of the 40X cases than the M70 cases when fire-formed (behind the .200 datum line). I have two barrels cut with the same .308 Win Palma reamer reamer to identical headspace and cases fired in the Remington will not chamber in the M70 . A small base die is used for both, but cannot size far enough back to make a difference.
Sometimes it's just easier to segregate cases...
