Barrel replacement is the Achilles heel of the otherwise excellent A-Bolt Browning. I think
the specifics of the problem, if memory serves me correctly
is that Browning's Japanese subcontractor uses a 'red loctite'-type thread compound when assembling the barrel to the receiver, and that because of this, removing the barrel can actually damage the action - the receiver threads come out of the receiver in such a way as to totally ruin the receiver.
So from what I understand Browning's answer to customers on this subject varies from: "if we rebarrel, we also replace the action
" to "our rifles are not meant to be rebarreled or rechambered
I understand that very slow and careful heating will defeat the loctite, but that is the reason that aftermarket barrel makers don't offer replacement A-Bolt barrels and the huge majority of intelligent gunsmiths don't want to take on a project that can easily result in a ruined receiver and an irate customer. It is not cost effective for the few they would sell.