Powder selection for RUMS

[sambo3006]

I got some responses for powder selection for the 7RUM a week or so ago. I have a 338RUM also. Am I correct in assuming that slower powders would work better in the 7RUM than the 338RUM due to the smaller hole in a big case?
I loaded up 102gr of Retumbo behind a moly 225gr AB in my 338RUM and was hearing some powder crunching when I seated the bullet (OAL to fit in the mag). This load is below max and avg velocity was 3006 fps from a 26" barrel. I would like to hit 3100 fps but don't like crunching powder. I bought some H1000 which is a little faster and looks to generate the same pressure with a few grains less powder. I'm thinking that the H1000 would work better in the 338RUM and the Retumbo would work better in the 7RUM--I'm going to use 150 gr bullets. What say you?

 

[Fiftydriver]

Sambo3006,

Here are the burn rate of powders I recommend to my customers for each of the RUMS. These are general recommendations meaning any powder with similiar burn rates will perform equally as well.

7mm and 300 RUM
H-1000
RL-25
Retumbo

338 RUM
H-4831
Rl-22

375 RUM
H4350
H4831

These generally get about all the performance you can get out of these rounds with a good level of load density.

Retumbo is pretty slow for your 338 RUM, especially with a 225 gr pill. Look at some Rl-22 and see what happens. I suspect you will be suprised at the performance level you get and load densities will be a bit more powder friendly when seating bullets.

Even H-1000 is a bit on the slow side. With 250 and 300 gr pills it would work well but not a 225.

Retumbo seems to be one of "THE" powders for the 7mm RUM. 300 RUM as well.

Kirby Allen(50)

 

[sambo3006]

Thanks Kirby. This is exactly the type of info I was looking for. I have both RL 22 and IMR 7828 on hand. The max load on the IMR website for 225gr 7828 is 92 gr. I believe this is with the 225gr partition, so it may be a little different with the AB. RL 22 should be similar. I'll back off some and chrono test my way up while observing for pressure signs.
Thanks again,
Sam

 

[Fiftydriver]

Should work well, keep us posted with the results!!

Kirby Allen(50)

 

[goodgrouper]

I agree with Kirby. RL22 works great in the 338 ultra mag and produces top velocities and usually top accuracy as well. Nosler number 5 shows faster velos with RL25 and the 225 grain bullets but I have yet to see RL25 shoot faster than RL22.

You could also burn RL22 in a 7 ultra in a pinch but your loading densities would be on the low side.