G'Day Fella's,

Gordon and Brithunter, I may be wrong (won't be the first or last time) but I would imagine that the Baikal barrel is probably Soft Soldered into the Monoblock and not threaded.
If you look at the outer circular joint between the monoblock and barrel in Brithunter's image of the open action, you can see this joint has basically the same size gap or line width from, 10 O'clock around to 5 O'clock.

If this was a thread (being helical), the gap or line would become smaller as it went around.

This being the case (???), with the careful use of a LP/Propane gas flame (Oxy / Acetylene is to hot), you should be able to heat up the monoblock enough to remove the original barrel, without damaging the blued finish on the monoblock?

Gordon, Welcome to this Forum!
I think you know an Old Mate of mine (D.N.), he's a hunting guide here in Canberra, Australia.
He regularly forwards your emails onto me. Thank you for them!
We could all profit from you hunting knowledge and experience.

Hope the above information, is of use/help to you.

HooRoo
From
Hommer