the barrel is part of the upper frame. Some smiths have cut them off and threaded the frame for a new barrel, but it's not for the faint of heart, it's a high skill job and won't be cheap. It's far more cost effective to have the barrel relined and the best option is to have it done in 30 mauser, to maximize the wall thickness of the liner. Still won't be cheap but will minimize the cosmetic changes.