Hi Mike, I have used 15 gr. of Unique in my 338 Win. Mag. under a 250 gr. LBT with complete satisfaction. As I recall, it chronos about 1500 FPS. Accuracy was exceptional!! Please use this load with caution, it was extrapolated from 358 Norma Mag data, but should be okay up to 18-19 grains. Ain't it a pain to find good .338 cast bullet data??