Not what you're looking for, but the 250gr Smkhp's didn't work in my .338 x .378 and the 300's do. A little closer to the question; 250gr Nosler Partitions work great in .340 Wby's. In general, I would think that the 250gr Smkhp's would be good in the .338 WM, but the 300's are too heavy to be optimum in that caliber. I would work on the 250's.
Good luck, Tom
Texas State Rifle Association Life Member
NRA Endowment Life Member
A big fast bullet will beat a little fast bullet every time