SR bbl.
Sir;
The thread size of the small ring Mausers is .980X12 at 55 degree (most smiths thread 60 degree).
As long as your shank can be turned to .980 you're home free.
But - generally the small ring actions are limited to cartridges of 45,000 cup. You need to inspect your action, cracks, lug seath, etc. before re-barreling!
I personall think that alot of SR actions will take more than that, yet, I wouldn't suggest it.
Harry B.