Well you would have enjoyed this evening in my garage. Except for the heat.
I made some barrel blocks and action blocks out of various pecan, cherry, and pine scraps I had laying around, set up the barrel in my bench vise and cranked the receiver off of it. Rbertalotto posted some good info on TA about the obscene amounts of threadlocker used to hold the barrel in place, I got it going fine with no heat but at 1/2 turn the stuff galled up and I did have to use a little propane heat to soften it. No problemo, off she came. The secret ingredient other than limited amounts of g-a-s turned out to be juniper rosin from my lovely local infestation (you may have noticed in my shooting vids). Used a mixture of sticky and powdered dry, rolled it into the barrel blocks with a junk '06 case and never slipped or marred a thing.
Hacksaw came next to remove 1.25" of the barrel stub. Then to the lathe for turning a little spot on the tenon for the steady rest, then setting it up again in the steady to face off the back side of the barrel cleanly for a better live-center pilot in what used to be the throat. I'll probably go ahead and turn off a little more before switching back to the tailstock center. Then I'll be finishing out the shoulder, thread minor, relief cut, and OD bevel before cutting me some metrico fantastico threads. Apparently they don't know what an inch is in Brazil, which might explain a few things.
The forward third of the barrel seems to have a hook in it, not sure but I'll take a closer look tomorrow in the lathe. If it does, I'm going to have to stop and try to straighten it before proceeding, or skip to the end with Freebullet's idea.
I took a couple pictures but will post them tomorrow.