300rum

Retumbo works great in the sendero barrels, RE25 in a stable climate, H1000 if neither of the others works out. This assuming you are going to be launching 200+ grain bullets....the only reason to burn 90+ grains of powder.
 
I've had good accuracy in my 300 RUM using Retumbo and IMR4350. IMR4350 isn't a powder most would consider using in the 300 RUM, but I believe Nosler stated in their manual they obtained excellent accuracy with light to medium weight bullets with that powder.

Retumbo is my favorite powder, however, in the 300 RUM.
 
Two friends asked me to help them with their 300 RUMs the last two weeks.

One rifle used H-1000 with 230 gr berger target hybrid. Ave vel was 2900 and very accurate.

Other rifle used US 869. 99 gr yielded 2866 fps with the 230 target hybrid also with excellent accuracy.

I used RL-33 in my 300 RUM and 230 target hybrid vel 2975 fps.

A friend's and his son's two 300 RUMs use H-1000 with both the 215 and 230 target hybrids.
 
+1 to H1000 and Retumbo. I would strongly recommend staying with a non temp-sensitive powder like Hogdons Extreme powder line. I was shooting some 230 OTM test loads last night w/ 93 grains of Retumbo (very hot load, don't start here) w/ a max velocity of 3129....my best accuracy was around the 2975 fps range though.
 
Rl 33. Then I would try 33 and if it didn't work out, I'd try 33 again. :D I've tried Retumbo, H1000, and 7828ssc. What I have found is all the powders work good. It depends on what your trying to achieve that will determine your final powder. For me, I wanted blazing velocity, long range accuracy and low pressures. After trying powders mentioned, 33 gave me the results I was after. My rum is a 27.5 inch benchmark Remington heavy varmint. 101.3 grains of 33 with the 230 Berger. 3200 fps. I have a friend I load for who shoots the 300 rum sendero. We load 102.3 grains of 33 with a 200 lrx bullet. He is just shy of 3300 fps.

I was so impressed with this powder I used it in my son's 270 wsm with a 165 grain matrix. No pressure with 71.5 grains. Accuracy is very good.

It's a fun quest, good luck!!
 
I concur with the others that rl25, retumbo, rl22, and rl33 are good powders to use in the 300rum. I also burn mil-surp wc872 and rl50 in my rifle. 180 grain and heavier bullets can use powders intended for the 50bmg in this caliber so you don't have to hunt quite as hard for powders as you do with the lesser magnums.
 
As was mentioned the new velocity king in the 300 RUM seems to be RL-33. I'm running the 210 Bergers with 97.0 grains at 3,040 fps (that is where it is accurate) and it is just loafing along. I'll probably get 10 reloads out of the brass. Shot a 0.500" group at 200 yards too so it has accuracy potential as well. I have noticed moderate temp sensitivity though not as bad as RL-22 or RL-25 which use a different technology and are really bad - unusable if temp is a concern.

Per test data on Barnes's website H1000 and Magnum were very stable over temp. I'm guessing Retumbo would be too. If temp is concern those are three good powders. My go to load in the 338 RUM uses Magnum. I've done the frozen ammo test on that rifle and it was rock solid. No drift at all. Now if I could just find some more to buy.
 
Rl 33. Then I would try 33 and if it didn't work out, I'd try 33 again. :D

I concur. I have a first edition 300 RUM Sendero with less than 50 rounds through it when I got it. I tried all the previously mentioned powders with most of the popular bullets. Not until I tried RL33 behind the 230 gr. Berger hybrids did I have any satisfactory results. I still have a lot of work to do but I've changed my mind on getting a new barrel.........at least for the time being. :rolleyes:
 
I ended up backing off more than a full grain due to temp sensitivity in 33. When it's a cool spring day, my max load is 102.3. When the sun is out, no way can I shoot 102.3. It went down 101.3 to be safe. 33 is a unbelievable powder, but it does have its draw backs. Temp being the major one. Here's a thread that can give you lots of examples of this.

http://www.longrangehunting.com/forums/f19/rl33-temperature-regression-thread-130521/
 
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