I would not hold my breath for a .338 bored barrel. I think that just about all the .338 comercially available (except the .338 Federal) are pretty high in pressure and have larger case diameters.
Personally, I do not like a stub for any cartridge, that a T/C Contender will not handle. The reason I say that is once you bore out a stub, the diameter left for the barrel is about the same diameter or a little less than a Contender barrel. I think you would have a better setup if you would have a smaller bore reamed out to .338, then the barrel would be full diameter. I think the .338 bullet is a good choice. It has a slightly larger shoulder than a 358 to head space on and the bullets have higher BC's. However, the 358/356 is an easy/cheap conversion for the 357 Magnum.
Good Luck and Good Shooting
