There are only a couple real option's , either Re-chamber a 17 m2 or hmr barrel , this is the easiest way ( cheapest too ) or you can have a barrel blank " Stubbed " into a donor barrel .
If one has the skills & machinery , a lug may be cut off another barrel and welded onto a blank , don't know if that one has been done much if any .
stimpy
PS Like Quick said !