I have several 338 RUMs and they like H 4831 sc , Retumbo and US 869 with 250gr
Accubonds.
With my rifles the velocity was over 3100 ft/sec (No Pressure).
I didn't have any luck with H1000 even though it looked like one of the preferred
powders.
Using the 225 Accubonds They liked the H 4831 sc best for just over 3200 ft/sec.
J E CUSTOM