I don't have a 338 Fed, but I do have an older 338-08 AI, pretty close to the same thing.
Regarding Fire forming, I just neck up 308 brass, load bullets to full charges and use them for practice.
For hunting I use the now fire formed brass with some version of Nosler, a proper amount of RL15 and go.
I have it because it came at a good price, I always have a good supply of .338 bullets and Reloader 15 because I have several other .338 rifles, and it will kill anything I'm ever going to hunt at ranges I feel good about, and it's a pure joy to carry in the high country.
Not claiming it's better than anything else, but it works OK..
