I just bought a 30" 12 Ga barrel for a Savage 720 / 750 / 755 off of ebay, but I realized after paying for it that it does not have a barrel extension. The beginning of the barrel is threaded with no way to mount into the reciever. I do have an existing barrel for my 720 (26" mod) and for my 755 (26" Imp. Cyl) .
How hard would it be to use the extension off one of these barrels? Thanks for any help.

Also, I can find an extension on Numrich for a Rem Model 11 but not for the Savage, could it be interchangeable? I always thought the 11s and the 720s were interchangeable. thank