Big 338 powders??

[lovdasnow]

Hey guys my 338 Rouge(338-378 improved) is getting finished up, and I need to get a few powders to start load workups.

will be shooting 300gr bullets. I like RL25, but would like more temp stability then it has.

what should my choices be? H-1000, Retumbo? anything else?

thanks again,

 

[Long Time Long Ranger]

Retumbo getting close and you can get some good loads with it but the others are way to fast for this cartridge with 300's. You will not get top velocity with powders faster than Retumbo. Look at a powder chart and pick out the slowest ones on there. If you can find any H-870 it is very good. H-50BMG, H5010 and the slowest Vihtavuori powders from 170 and slower. I haven't tried US 869 but it may work.

 

[lovdasnow]

great, thanks. are those powders you listed pretty temp stable?

 

[backwoods83]

retumbo is probably the most stable of the powders mentioned, this might sound insane but with the pressures that case will hold id start with some tame loads of imr 4831 and work up 1 grain at a time, velocity may slighly suffer, but you cant beat consistency! want more speed RE22 or imr 7828ssc. good luck!

 

[BountyHunter]

MRP2 is same burn rate as RL 25, but lot more stable. I have used it in the 338 AI quite well.

BH

 

[Long Time Long Ranger]

lovdasnow, I currently have seven 338-378 weatherby's I built when it was a wildcat well before it became a standard cartridge. My data on the 338-378 wby alone would make a good book. I have extensive data with most reasonable powders on bullets from 185-325 grains shot on my range. Powders faster than retumbo limit the velocities attainable with this cartridge. Send me a PM and I will get you some data. Yours would shoot the same powders best just more of it with better velocities. I am not familiar with your improved version but the 338-378 wby imp is certainly at the top of the big 338 spectrum. This huge case having the ability to utilize massive doses of super slow burning powders is what puts it well ahead of the various offerings off the ultramag and lapua cases.

 

[HighKnob]

Weidner's has WC 867 and 872, new military powder for $49 for 8 pounds. I've read some good reports using it in mag calibers with heavy bullets. Been thinking about trying some in my 7 mag, but it's on the low end of this powder with 140 gr. bullets. It's slow and very stable from all I've read.

 

[wc872]

I can only speak of the 338 Lapua Imp. I tried several powders & the one that worked the best for me was VV 24N41. I was able to get the best velocity & accuracy with a case full. RL25 came in second in the velocity & accuracy dept. While one could use WC872 I found it to be quite temp. sensitive. I had such good results with 24N41 that I just kept using it. While I don't have the rifle anymore I do still have about 2 lbs. of the second 8 pounder. When I tried N170 it acted like a lot faster burn rate in my rifle. H50BMG was ok but nothing to really get excited about.
Semper Fi

 

[lovdasnow]

thanks a lot for the info guys. i feel like i'm weeding a few powders out that i may have tried.

those VV powders sound interesting for sure. anyone else out there having good results from them?

thanks

 

[RDM416]

lovedasnow, I have been shooting 338/378s and 338/378 improved (338 Kubla Khan) for several years and have tried a lot powders.

For best velocities I keep coming back to RL 25, although it is not the best for temperature stability. I have done qute a bit of temp testing and it is fairly easy to compensate for in typical conditions.

I am currently working on some loads with Retumbo and have drawn no absolute conclusions yet, but it looks like RL 25 will win in the velocity race.

In my experience US869 and H50BMG are too slow. I have a 30" barrel on one of my Khan's, but still have not been able to get these real slow burning powders to even come close to the same velocities as RL 25 or Retumbo.

 

[Long Time Long Ranger]

Well I guess we learned something here. It just depends on the rifle evidently. I have never got RE-25 to match the performance of the slow burners in the 378 case. Always pressure signs before top velocity in mine.

RDM416 are you talking about with 300 grain bullets? I guess that just goes to show you need to try them all and see what works in your rifle.

 

[RDM416]

LTLR, Yep, for me RL 25 gives me the best velocities with 300 SMKs, although the difference is more pronounced with 250s. US869 and BMG are the only really slow powders I have spent any time with, but I just can't seem to get good velocity from them. I had some loads with BMG that seemed to be very accurate but I did not work with it enough to be sure since the speeds were not what I wanted.

 

[Kiwi Greg]

I use Vit N570 in my Lapua Improved.
I can use the same amount of Retumbo but the Vit has more speed, I tried H50BMG, US 869 & 24N41 but they weren't as good.
I have a 33.5 barrel & get 3120fps ish with single digit es according to my 35P.
The brass doesn't like it much but the primers still seat fine
It is built on a Rem 700p & I'm very happy with it, accuracy is stunning

 

[Long Time Long Ranger]

Just so everyone reading this knows. There is a world of difference between loading the lapua and ultramag cases and loading the really big 338's off the huge 378 wby, 416 Rigby, Excalibur, etc cases. The lapua and ultramag based cartridges perform best with a faster burning powder than the big cases. They just can not hold enough of the slow burning powders that make the big cases shine. For all the 338's I load off the lapua and RUM cases powders with burn rates from around 7828 to Retumbo work best. WMR was the best I used when I was working with various improvements to the Lapua and RUM cases back in the 90's but they quit making it. With powders available now I get best results with powders that have burn rates similar to RE-25, H-1000 and retumbo.

With the huge cases I have got best performance starting with Retumbo on the fast side and going slower. H-870 is the best I have used for the big cases and it outperforms any faster powder by up to 100 fps or more. Problem is they discontinued it. With powders faster than Retumbo I exceed pressure limits before reaching maximum velocity.

Not saying that powders outside the burn rates I listed will not shoot well in your gun. I am saying it is best to work within the burn rates that give optimum performance and top velocities. Then when you hit that perfect load you are getting all the velocity performance you can out of your rifle.