Rate of twist for 338 lapua magnum?

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xopher

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I am looking to step up from my 308 this season and experiment with the 338 lapua magnum. After doing load development last season, I was fed up with trying to balance muzzle velocity and BC in hopes of getting the bullet accurate out to 1000 yards. Yes, its entirely possible, however, i'd rather try with something thats capable of nailing a milk jug sized target at 1000 yards.

After doing research myself, i noticed everyone had their own preference when it came to the twist of their barrels. Some liked the 10, others 9.4, 9 and so on. Unlike 308 where most people prefer 1 in 10 or 5R, I can't seem to find a clear answer for 338.

What do you guys use?

Oh yes, before I forget, I plan on shooting heavy 300 gr projectiles. Please let me know if im going in the wrong direction...
 
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Just read an article by Todd Hodnett about barrel twists and from the testing he's done faster is better. When he says faster he means lots faster. Haven't got it in front of me but they we shooting .308's with something like 1:4 or 1:6 barrels. Traditional concerns were bullet failure, increased pressure and velocity loss. With modern bullets failure isn't a concern, and tests have not shown any pressure or velocity issues. He said you can't over stabilize a bullet, and when it goes through the transonic range the more stability it has the better it will perform further past that range. He definitely challenges conventional wisdom and backs it up with real experience.
 
I wonder if Todd shoots F class?

338 cal 10 twist. There is no bullet on the market today that needs a faster twist.

Jerry

PS, the most unstable a bullet will be is within the first 100yds. The further it goes, the more stable it becomes. The vast majority of modern bullets have no issue going transonic. Overspinning have a serious negative affect on flight and accuracy. Give Bryan Litz a read. We back it up with tens of thousands of bullets sent at paper targets. Ironically, the trend is to slowest twists......
 
He seems to be more interested in what bullets do well beyond F-class ranges. Yes the further a bullet goes the more stable it becomes to a point, once you start loosing rotation bullets do become unstable. In his article he noticed .308 bullets hitting sideways (can''t remember the range) which made him try a faster twist and that sorted the problem.
 
At 2000yds, I doubt there is a single bullet that is still supersonic. We shot just fine from 1 mile on out with a fairly diverse range of bullets, twists and guns.

He is mixing up aerodynamic and DYNAMIC stability.

There really has only ever been 1 really bad example of bad DYNAMIC stability which is the Sierra 168gr MK. Well documented.

I have shot a very wide range of bullets and all do just fine going subsonic in standard twists.

best way to prove it to yourself is launch a few at the horizon. A ballistics table will give you a rough idea of when the bullet should go subsonic. Shoot at a distance 200 to 300yds FURTHER just to give it time to tumble and see what happens.

I even tried to underspin bullets just to make them tumble when they went subsonic.... no joy. If they were stable in the first 100yds, they didn't seem to care going subsonic. At least, I never bumped into 1 that did. I only focus on LR match bullets where instability is a big problem on target.

There are UNSTABLE bullets. But that has everything to with bad design and these were funcky at all speeds and twists. They dont stay on the market very long.

If he has found examples, love to hear about it.
Jerry
 
In our builds we have found that 9 or 9.4 works extremely well with the 300 gr bullets. 10 can work with them but it is a little more hit or miss with the 300s for extreme long range stability.
 
Savage 110 BA 338 LM have a 1:9 Good for 300gr

savage110ba01.png
 
Sorry to get more off topic but I find this interesting as I have also found that the designer of the 300 Norma recommended an 8 twist for use with 230 Bergers for the same reason ( more accurate at long range) even though Berger says a 10 twist is good. I was of the same understanding that bullets became more stable further out.
 
Weatherby Accumark 338 Lapua is 1 in 9.3 , the TRR Weatherby is 1 in 10 twist. The Accumark can handle heavier bullets of a hunting variety as well as the 250 match bullets.
 
Unless you want to push a heavier bullet FASTER, like out of the Lapua Improved chambering, I see absolutely no use for a faster twist other than 1:10 in the standard 338 Lapua. Pushing a 250gr projectile at modest velocities (2900+ ish) is all you need to do to make these rifles work very well at any distance you want to shoot at. Heck, even a little past the 1 mile mark if that's your game.....
 
Mystic Precision said:
I wonder if Todd shoots F class?

338 cal 10 twist. There is no bullet on the market today that needs a faster twist.

Jerry

PS, the most unstable a bullet will be is within the first 100yds. The further it goes, the more stable it becomes. The vast majority of modern bullets have no issue going transonic. Overspinning have a serious negative affect on flight and accuracy. Give Bryan Litz a read. We back it up with tens of thousands of bullets sent at paper targets. Ironically, the trend is to slowest twists......
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I don't quite have the experience that you do but from reading this, http://riflemansjournal.########.ca/2010/06/ballistics-heavy-bullets-in-113-twist.html I have to disagree. Instability coming later in flight while still supersonic. Doesn't make sense as the bullet will slow down faster then it loses its spin but it shows on target.
 
Interesting article and German does a TON of testing.

The main point was to see if under spinning his selection of bullets would lead to instability issues. Conclusion .... NO. All bullets used in the test made it to the target even at 500yds.

It started that this was not an accuracy test yet, a random load that shot well at one short distance was also expected to shoot well at all distances.

Do any LR load tuning and you quickly see that load tuning has a massive effect on grouping and most importantly vertical. Small changes in the charge weight can have dramatic results on target at distance. 100yds is not where I do my LR load testing cause in general, it doesn't tell the whole story.

The goal of the orig test was proven. Lower then 1.4 SG may not necessarily mean doom and disaster. You just need to confirm WITH YOUR COMBINATION UNDER THE CONDITIONS YOU WANT TO COMPETE AT.

Sure most of us can't jet around the world testing at each range so we go by rules of thumbs and common sense. BUT, see that a 13 twist was used to launch a 200gr bullet at LOW MV and the bullets made it to target. THIS is the point.

So how to we move this experiment forward? Simple. Take 1 bullet that a shooter wants and feels is competitive in their sport. Take barrels from 1 manf of varying twist rates and tune for the best accuracy. Now shoot at distance and see what helps you score the best.

What I have found is that EACH bullet has its own likes and dislikes. I no longer say that a certain WEIGHT needs a certain TWIST. I say a certain BULLET launched a certain way needs a certain stability factor under these CONDITIONS. No, my testing is not exhautive but the bullets I compete with have been tested.

Many bullets will fall into the same ideal twist so 1 barrel can serve the needs of many uses.

Given the range of shapes offered in any bullet weight (see 30cal bullets if you want to be totally confused), a competitive shooter will tune to the specific needs of THAT bullet.

As I said earlier, the bullet has to be spun ENOUGH to make it to the target. I never said what enough was.....

To add more confusion and variables on the whole precision balancing act, look at the effects of bullet spin rates and :

crosswinds
Pressures and velocity
bullet accuracy - ie internal imbalances
"Tipping" I believe that is the jargon

OMG, how can I ever figure this out? Well, the end result is simple - send lead down range and see what works for you.

As German indicated, he would never have deliberately shot a 200gr in a 13 twist. His normal choice would be 11tw. Yet, under 1 set of conditions, the "odd" twist yielded results far more positive then expected. Compare the SG values

There is a HUGE SG range that works but what is optimal?

Holes in paper tell you all that you will ever need to know... just make sure it is as far as you will compete.

Jerry
 
.284 said:
Sorry to get more off topic but I find this interesting as I have also found that the designer of the 300 Norma recommended an 8 twist for use with 230 Bergers for the same reason ( more accurate at long range) even though Berger says a 10 twist is good. I was of the same understanding that bullets became more stable further out.
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Manf and bullet makers will always be conservative on their twist rates. They simply have no interest in dealing with poor feedback on that 1 instance where things dont work.

Why has the standard 30cal twist been 10 since the begining of time when no military rifle has ever been designed to shoot a bullet that need anything faster then a 12 twist?

Why is the present AR's speced for a 7 twist when even some 90's can work in an 8 or 7.7 twist?

Why do so many Rem chambers have throat so long?

No brainer, no muss, no fuss, no problems. But is the options optimised?

That is where fussy precision shooters come in and muck about with every single spec and tweak things to the nth degree.

The only service rifle I have seen that was optimised or at least set up better to max their service ammo is the SAKO TRG. Older ones are speced with an 11 twist. WHY? Cause the 338LM is a 250gr chambering pushing at 2950fps nominal. There was no 300gr option to worry about. At 1 mile, the ones I have seen shot did just fine with their 250gr loads.

Exactly as the rifle was designed to operate in service..... nice.

Jerry
 
This is a direct quote from Brian Litz, Berger's chief ballistician:
http://bulletin.accurateshooter.com/2010/05/berger-bullets-releases-new-338-hybrid-dual-ogive-bullet/
Practical Considerations — Load Length and Twist Rate
The superior ballistic performance of the 300gr Hybrid .338 is primarily due to the very long ogive and boat tail. However, that super-long bullet length can create some issues. Berger’s new .338 Hybrid bullets are so long that loaded rounds may not fit some magazines comfortably, unless you deep-seat the bullets, which cuts down on usable case capacity. If your loaded rounds with the new .338s are too long for your magazine, single-feeding is recommended. In addition, and this is IMPORTANT, to get optimal performance with the new bullets, you may want to extend the throat in your chamber. This can be done relatively easily by a competent gunsmith using a throating reamer. We caution, however, once the throat is pushed out, you can’t go back to a shorter throat without setting back the entire barrel.

The new .338 Hybrid bullets should stabilize well with a 1:10″ twist at the velocities achievable with popular .338 magnum cartridges. However, according to Bryan Litz, Berger’s Ballistician, at extreme long ranges (beyond one mile), as the .388 bullet goes trans-sonic, it may need more spin. As the bullet slows down into the trans-sonic range, extra stability is required — something you get by spinning the bullet faster. So, for those guys planning to shoot at one mile or beyond, Berger recommends a faster twist-rate. The faster twist provides more spin-stabilization at very long ranges. But for 1000-yard shooting, you don’t need to be concerned about trans-sonic stability. As Bryan explains: “So as long as you keep your shots under 1 mile, the 1:10″ twist is plenty adequate.”
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You should use Berger's recommend barrel twist and might even consider writing to Walter Berger directly for advice!
(I did for my 6x47 Lapua and ended choosing a non-standard 1-7.5" twist)

Alex
 
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