Easiest is to get a set of Redding 338/300 RUM dies. Others have used 338 RUM dies. Either one will neck size for you. That's about all there is to it.
just contact Shawn C, @ defensive edgeand you will be able to get FL dies for 338edge
all you need is 300rum Brases, fl with 338edge die, and then use 338edge bulet seating die.
easy and a lot cheaper than 338lapua.
shawn will help you with all the extra question and dies, plus the info for powder reloading.
best to go is h1000, 338smk, cci250m primer.