I had been wondering if a threaded sleeve would work. I am building up do do stuff like this (got a lathe this summer but not there yet). It seemed to me that a helicoil type idea would work. I was thinking leave the barrel as thick as possible, but turn off the old threads, and turn in new ones. Then inside thread the sleeve to match the barrel leaving it longer than the shank, then with sleeve threaded on tight and locktighted, turn and thread the outside. So long as the sleeve is thicker than the threads, it would seem the threads would be the weak link. Enjoyed the discussion.