H335 works well for 338 Federal using bullets from 160gr to 215gr. It is the second best powder for optimal velocity; and highest velocity is with Accurate 2230. These two give 100fps more than RL15, Varget, IMR4895, etc. Also significantly better than RL-7 and RL-10X. See my loads on Reloader's Nest for all the above powders in 338 Federal.
.338 Federal @ www.reloadersnest.com