A buddy of mine has a .338 Rem. Ultra Mag Encore barrel. He got it from MGM (Match Grade Machine) and it is a real shooter. I do know that about 6 months after he got it MGM ask him to send it back because they were having some problems with the barrels. His original barrel was fluted but I believe that they replaced it with a non fluted one. I would assume that if they could make an Ultra Mag. that they could also do a WSM. I believe their barrels start around $400. neald was correct about the larger diameter case and the problems associated with that. There is also little (if any) advantage to the shorter length of the short mag in a single shot so there is a lot of risk (and $$) with very little reward.
TP