Have you ever heard of stubbing a gun?
The existing barrel is cut short and threaded to fit the new barrel
The new barrel is threaded and fit inside the old barrel stub.
Yea its work but it works.
You could also cut the chamber off, rethread the barrel, and rechamber it. Dunno if there's enough meat on that end of the barrel to have enough diameter.
I guess you could also cut only part of the chamber off, leaving enough of the existing chamber to recut for .44 mag.