Re: 338 Rum & RL33 ?
Alliant doesn't show many RL-33 loads. You will have to do some comparisons using 338 Lapua data which IS listed:
338 Lapua 250 gr sierra mk, 103.5 gr RL 33 @ 3001
338 Lapua 300 gr Sierra MK 97.5 gr RL 33 @ 2748 fps
I had to figure out what to use with the 6mm-284, 7mm/375, 300 RUM and 257 Weatherby when it I got my hands on RL-33 over a year ago.
My conclusion is to start with a midrange or slightly above midrange load data for Retumbo and work up from there.
Based on my experiences RL-33 works best with the heaviest for caliber bullets.