I don't have much experience with .338's, but, a couple of years ago we took my uncle elk hunting, he was shooting a 338 win mag. He was shooting federal premium 250 grain noslers. He was taking about 500 yard shots, in about a 5 mph crosswind, and we could see were he was hitting pretty good. (He is a pretty terrible shot and hunter, but trying to get him half way close was a nightmare--long story.) I really like the old nosler partition load, if I had a 338 I'd start with trying to match that. I hope this helps!