New barrel .338LM

[6MT]

Ok, I have a new barrel on my .338LM. Since Retumbo is unobtainium these days, I’ve decided on using IMR4831 powder. (Mostly because I found a nice supply of it.) The bullet is the 300gr SMK, brass is Lapua, and primers are Federal 215m magnum. The new barrel is finished at 31”, and is a 1:9” twist. This rifle is used only for extreme long range (1500 metres and beyond). And I single load, so mag length is moot here. (In other words, I load ‘em long.)

On the Hodgdon site, it notes charge weights between 68 to 76 grains of the IMR4831 powder With a 300gr projectile. I would like to see speeds in the range of 2800 to 2900fps. I was getting 2880fps with the old 26” barrel and 93.6gr of Retumbo. Which was a pretty hot load. It was very accurate and I had great success to the mile and out to 1900 metres. I will maintain a .010” jump for seating depth, like I did with the first barrel. Since it seems the reamer that was used has given me the exact same CBTO with the 300gr SMK bullet As the first barrel (talk about luck!).

I‘m thinking I don’t need to go that stout since I have 5 more inches length on the barrel. (To try and at least maintain that speed of around 2900fps.)

Who has tried a 300gr bullet with IMR4831? What charge weights did you try? Barrel length? Jump? What were your results?

I am leaning towards starting out around 70gr and working up. What say you?

Andy 6MT

 

[SKWERLZ]

I doubt you’ll get 2900 with that fast of powder

2900 is tough enough to get with retumbo in 338 lapua, you had to be stepping on it pretty hard to get it.
imr4831 is a lot faster burning than retumbo.

 

[Drop Port]

^ this, I would be looking for some H-1000, R-22, R-25, R-33 and bunch of others before 4831.

 

[littlebuddybr]

Exactly what post #2 &3 said.

 

[Catfur]

Ramshot LRT (a PB Clermont ball powder) is made for 338 Lapua, and substantially less unobtanium than Retumbo right now.

 

[bozo699]

I haven’t tried H4831 Retumbo and H1000 worked well but my best loads was with RL33
Wayne

 

[6MT]

I doubt you’ll get 2900 with that fast of powder

2900 is tough enough to get with retumbo in 338 lapua, you had to be stepping on it pretty hard to get it.
imr4831 is a lot faster burning than retumbo.

Yeah, I know. It is probably too fast burning for the 300gr bullet. And velocity will suffer, even with the longer barrel. At maximum charge weight, the 4831 will be hard pressed to reach 2800fps IMHO.

So I managed to find some N570. I will have to wait a couple of months to get it (early May delivery). But that's just the nature of the beast up here in Canada. The only good thing is that it's still cold up here. I had not planned on doing load development until temperatures rose above 50deg anyways. And for those of us above 53° NLat, that's usually late April or early May.

Thanks for the input!

 

[SKWERLZ]

N570 is an excellent choice