Sarg, may have to rebarrel your rig - shame its a beauty!
We used to have Sprinter arms here in SA that rebored rifles, might be lucky your side of the ditch!
Apart from that I guess if you could send to the US it would be able to be done easily, plenty there - but importing/exporting a barrel?
Might be an option - albeit expensive one!
best of British
93x64mm