If you have a rifle re-chambered, say from 458 to 450#2, would you also have it
re-proofed? YES

Would you buy a rifle that had been re-chambered that has not been re-proofed?
NO

Would you buy a rifle that has been made by a gunsmith on a shotgun action that has
not been proofed? NO

Would you pay the same for an un-proofed re-barrel or re-chamber as you would for gun
built as is. NO

Mickey,
Some of these questions are arbitary as it's really only the US, Australia and a few others
you can get away with this. Like a Cogswell & Harrison 375 2 1/2 rechanbered to 375 Fl Mag.

Each to their own.

500 Nitro