I guess that I'm a little more direct than maybe I ought to be so don't consider this as being mean, just straight forward.
IMR-4350 is too fast for your cartridge and bullet combination. JUST C has pointed out the more appropriate burning rate powders for the 300 RUM. I would add that you can also try:
V V N-170
MagPro (I haven't tried this yet)
"MAGPRO A slow burning, double base, ball-type rifle powder developed specifically for all the new Short
Magnum calibers of both Winchester (WSM) and Remington (SAUM) except for .300 SAUM. This powder
excels in the 7mm WSM
as well as the .270 WSM and even derivatives of the wildcat 6.5 Short Action.
Excellent in all overbore magnums such as the ULTRA magnums from Remington i.e. 7mm RUM, .338
RUM as well as the high performance .338 Lapua Magnum. Excellent flow in progressive auto-loaders
and volumetric dispensing equipment. This is THE magnum rifle powder to have."
You can do a search here and get some other suggestions from previous posters for surplus powders that will work, as well.
[ 04-05-2004: Message edited by: Crispin Goodall ]