Rolling Block bbl. change.
Dear STEVE 123:
On any rifle changing a barrel is serious business. First, you need to make sure there isn't a pin or screw locking or holding the bbl. in the threads. If not then nmark a witness mark on the bottom of action and bb'. Then using the proper tools unscrew bbl. In cutting a new one measure the shank length, diameter, and thread pitch. If the threads are close then make your bbl so it screws in with at least a 75% thread (it will hold 90% of a 100% thread will). Then the extractor groove must be milled properly etc, and the chamber cut.
This is just a general description - it;s not meant to be smart or pedagogic, but just to give you some info - if you're not familiiar with lathe work you really shouls find a GOOD smith.
Happy fiddling! Harry B.