The .300RUM is a great LR hunting cartridge. Mine has taken 3 elk, and one mule deer. And rang steel out to 1350 yards consistently.
I have had one since they first came out back in 1999, and have been reloading as soon as dies were introduced, way before there was any load data available. I just weighed the water capacity, and started light, working my way up.
I have had a few different loads over the past 16 years, and I am still on my first factory barrel, a 26" 1 in 10" twist with a KDF muzzle brake. I don't think the statements of, "If you install a muzzle brake, it will kick like a .243" are quite accurate, but they help tremendously. My 12 year old daughter used mine last November to take a great AZ bull elk.
Here are a few of my more accurate load recipes, but you need to start light and work your way up.
Rem brass
Rem 9 1/2 Mag primer
Barnes 175 LRX
88 gr. RL22
3.844 COAL (does not fit in the mag, so it is a single load round)
3361fps
.417" @ 100 yards, 3" @ 500 yards
This is the round my 12 year old daughter took her bull elk with last year. Elk never even twitched. Instantly DRT.
Rem brass
Rem 9 1/2 Mag primer
175 Sierra Match King
88.2gr. RL22
3.710 COAL (Does not fit in the mag, so it is a single load round)
3298fps
.344" @ 100 yards, 8" @ 1350 yards
http://s642.photobucket.com/user/la.../IMG_20130529_193552_937_zps1f5c4108.jpg.html
My favorite hunting photo so far.
Rem brass
Rem 9 1/2 Mag primer
86gr. RL22
210 Berger HVLD
3.860 COAL (again, single shot round)
3030fps
.388" @ 100 yards, 6.1" @ 1000 yards
Rem Brass
Rem 9 1/2 Mag primer
86gr. RL22
215 Berger Hybrid
3.870" COAL (single shot round)
3010fps
.285" @ 100 yards, 2.10" @ 500 yards, 5.8" @ 1000 yards