Question: Limitations for a 1/12 twist in 338 Lapua please. Thanks, Jerry

Why would you want that twist? You will be limited to lighter bullets. I would want a 1 in 9.5 at least.

Boom, Thanks for reply. What is considered a lighter bullet? Would a 1/12 stablalize a 250 Gr. bullet? Thanks again. Jerry

quote:

Originally posted by jerrys9:
Boom, Thanks for reply. What is considered a lighter bullet? Would a 1/12 stablalize a 250 Gr. bullet? Thanks again. Jerry

A 250 grain all-copper bullet probably needs 9" or 9.5" twist. See the Barnes site on .338" data. They also make 285 grain bullets that are 1.79" long and need fast twists.

1 in 10 is going to be the slowest twist you would want with this round up to maybe 275 grain bullets. Most that I've seen are 1 in 9 or 9.5 which will allow shooting the heavier bullets that it's made for. 1 in 10 would be fine for 250 grain bullets if that's what you want to shoot.

Ken....

What is the purpose of the rifle?
I don't see any down side to a 1 in 9 or 1 in 9.5. I'd you want to shoot the heavies then go for a 1 in 9 and you could shoot about everything.

I use primarily 300-grain Scenar Lapua projectiles in mine, which is a 1:9 twist rate. Savage has also went with this as their twist rate for the .338 LM lineup they have, in expectation of heavier bullets being in the works.

You will want to stick with the lighter bullets. One manufacturer (IIRC Hornady) makes a red polymer "ballistic-tip" in 225 grains. The problem you will encounter is bullets in the 225 range do not offer you the ability to make use of the Lapua's range abilities. I tried these lighter bullets, and found at 100M (for zeroing), my groups were significantly larger than with the heavier weights. I assume this was from twist-rate being too fast for the lighter projectiles, but am unsure.

Lapua also makes a lighter load, in the way of the 231-grain Naturalis, which is marketed as a hunting round.

Hope this helps.

I am going out on a limb here:

To what purpose are you shooting the 338 Lapua?

If the answer is ultra distance shooting then one has to ask the question what bullet exactly ?

Once that is answered then the twist can be optimized.

The twist must give just enough revs to keep the bullet at a SF of about 1.3 and no more.

That gives the best possible balance between stability and tractabiity for the chosen bullet. Very much at issue in ultra distance shooting.

A "to fast twist" barrel for a given bullet weight on long distances gives relatively poor tractability which negates any potential benefits you would have gained from the cartridge bullet combination in the first place.

The 1:12 is actually the optimal twist for a 250 gr bullet for ultra distance shooting for the 250 gr bullet as that would give the least amount of drag on the bullet.

Shooting the same bullet from a 1:10 or 1:9 on the Lapua would actually lead to more drag and hence a less opitmal flight time and path.

I had one of the first Sako TRG-S Lapua rifles, it had a 1-12 twist. The Lapua factory 250 grain ammo was very accurate.