Well, I took the plunge.
As all of us Sportco 44 fans know the Australians are using the original way of having locking lugs inside the barrel instead inside of their receivers.
I cut off the old, old Sportco 44 308 Win barrel (over the weekend) 1.5" in front of the chamber, bored it to 7/8" dia and 1-1/8" deep and threaded it with 15/16"x20tpi thread creating the adapter for the next barrel. Then instaled the heavy (Ken Jones (?)) 26" long and 1-14" twist barrel chambered for 225 Winchester cartridge.
I decided on 225 Win b/c it's little less fat, fits existing bolt face and creates less erosion inside the the barrel than 22-250 but has more long range performance and feeds better from the single shot action than the 223Rem would.
Hornady #3 and Speer #13 used the 1-14" twist barrels in their manuals to handle 60 and 70gr bullets at 3300-3500fps in 24" long barrels so I think I am on the right track and propably the only shooter in Canada with LH Sportco 44 in 225Win!
I can't wait to take the rifle to the Heffly Creek range once I have more spare time when weather improoves (cold....up to -20 so recreation shooting is no fun anymore....).