Both my .270 WBY and my .338 Win Mag love Vihtouri N 160 powder. As for bullets, I favor the Nosler Partion 250 grain, but you can't go wrong with the Barnes and A frames either. The only bullet failures I have ever had were with the A Square, but you don't see them around any more.
The 338 WBY is an really flat shooting hard hitting round that will take just about any critter that walks the earth, but I would seriously consider a muzzle brake if you haven't already. Recoil is not just foot pounds. I am not generally recoil sensitive, but found the .338 WBY hurt more than the .460 WBY. Don't get me wrong, the .460 WBY has more recoil, but I would describe it as a hard push, while the .338 WBY was a sharper almost stabbing pain. I am told that a muzzle brake cures the painful recoil and i believe it, but I would try that out before buying one.