Sure you can weld up the barrel and rethread it.
Gun barrels are not hard.
Bob Sander of Sander Custom Gun Service would TIG weld up the threads of 03A3 and recut for Mauser threads.
Seen him do it several times.
Yeah I know "you can't do that it will ruin it "
CW Shooters Supply Inc
Machine Shop and Finishing Services to the trade and public