The better gunsmiths can headspace a new chamber to match that of your old barrel within a thousandths +/- .
Think I have 8 BRA barrels that share the same brass, chambered off the same reamer by the same gunsmith. This coming weekend i plan on taking my actions out to him to chamber up another 6 barrels for next season. With the actions in hand I've never had a chamber headspaced with any measureable difference.
I can swap a barrel in 15 minutes, 30 if I really get carried away cleaning things up and torque to 60 ft/lbs and get repeatable head space every time. I routinely shoot rounds in one barrel loaded for another with only the seating depth being off from varying throat erosion.
l bet I have over 1000 pieces of brass that shoot in any of these barrels and will shoot in the new ones too.
I have heard but dont know if theirs truth to it or not that brass shot in one chamber will retain a memory so to speak and when fired in another chamber it will go back to the size it was when fired in the original chamber.. not sure i buy that as i have used brass in multiple chambers before with no problems. Just something i have read on the internet so you know it must be true.. 😏
I had heard this as well but have not seen it my somewhat limited experience. I guess the test will be what the brass does after it is fired. It it continues to mis-behave, then there may be some truth to it. If it is true then it seems that replacing barrels would be a real problem since all the brass would need to be replaced....hard to believe that this would be the case.