I bet the barrel is removed and the cone is welded up and recut on a lathe....
I don't think so. You can't remove the barrel if the forcing cone is
expanded, which it will be if its cracked or blown out of shape. Trying
to get the old barrel off, without cutting off the forcing cone, will
more-than-likely break the frame.
He has to cut the forcing cone off, to remove the barrel. I had him
work on two early K-frames, with blown-out forcing cones. One, he
just replaced the barrel.
On the other, he did a very intricate sleeving job. The sleeve itself
became the new forcing cone, and the threads for screwing into the
frame. The old barrel became a shell, that he threaded internally
and screwed onto the sleeve. The workmanship was great, and it
was very difficult to tell, from the muzzle, where the sleeve met the
original barrel.
Later, Mike Priwer
