Seems like the 300 RUM folks really like Hodgdons new RETUMBO extreme powder and Alliants new RL 25 for this cartridge.

I have a brother-in-law that just started working with his and he is getting right at 3400 fps with RETUMBO and 180 grain Nosler Accubonds. We don't know what the accuracy is like yet, but based on the experiences of others on this site I am sure he will find something to his liking.

I'm looking for a powder to use in a .300 RUM that will push my 180 gr. Swift Scirroco bullets at around 3400fps(or more) and still allow for 1/2" groups at 100 yards.

Thanks for the help.

I have reloaded for 4 300 RUMS and found Retumbo to consistantly be the fastest powder in every rifle. I never reached 3400.
I would recommend that you try and reach around 3300 with either RL-25 or Retumbo.
If you reach 3400 unless you have a longer than 26inch barrel you are probably running too much pressure.........DJ

3400fps and 1/2" groups are not all that realistic unless your barrel is more than 26" long and your rifle is a very high quality gun.I have two 300ultramags with 26" barrels and neither will reach 3400fps.Neither will do better than 1-1/2" groups with scirroccos either although both average 1/2" to 5/8" with 180gr ballistic tips.I am using r-25 in both guns.

With retumbo I shoot 200 grain speers at 3200 ,220 sierra MK at 3050 ,and 240 MK at 2850 in my 26" winchester.

The only 180 grain bullets I have shot have been remington partition factory ammo at 3320 fps.

I have not shot any groups.

One of mine will shoot Scirrocco's very well using RL-25 but at a little under 3300 -still plenty fast enough. Retumbo shot them faster but not as accurately -I'll take very accurate and fast enough.
I've had 2 of them that have shot bugholes with the 200gr Accubond. I'm still refining my load for 1 rifle but I'm beginning to think the 200gr Accubond might be a great bullet in the 300RUM. - My buddy shot a nice Elk with the 200gr Accubonds I loaded for his 300 RUM last year. I'm also messing with 180 Accubonds and 180 Triple-Shocks, but if I get a couple more groups like I've been getting with 200 AB's I'll quit there.......DJ

Err, that's a bit higher velocity than any manual lists. Sure 3400 is safe? (I'd love to hear the load details; I have a hard time getting 3300 out of my 26" tube.)