Faster or Slower?

[Paddyd]

For a .308W shooting 150-155 gn bullets, which is better suited? 1/10 or 1/12 twist?

 

[ShootDots]

If it is JUST 150-155 class bullets, a 1-13 is best! I used to shoot a .308 that had a 1-13 and it shot Berger 168gr boattails phenomenally! If it shoots the 168 perfectly, it sure will shoot a 150 class bullet. The slower the twist that still stabilizes and maximizes B.C. will not magnify flaws in a bullet like a faster twist than what is necessary could.

 

[Zero333]

I've blown up bullets with too much twist.

But I've never blown up 155's in 10" twist 308win rifles.

I'm inclined to partially agree with @ShootDots .
If you know 100% for sure you will never shoot longer bullets than 1.22" in the 150 / 155 gr range, than 13" twist is the smartest choice.

If it was me in your shoes, I'd settle with a 12" twist. This way I'd have flexibility with bullet choice.

 

[DaveTooley]

At 308 velocities you won't be able to see any difference in accuracy from a 1-10 to 1-13.

 

[Larryh128]

I have a 12 twist and it shoots 155 gr bullets very well.

 

[natdscott]

At 308 velocities you won't be able to see any difference in accuracy from a 1-10 to 1-13.

UNLESS it is a 30" tube. Even so, at only maybe 225,000 rpm, and with a relatively short, rigid bearing surface, I cannot think you'd see any issues. It's just not that fast for a modern match bullet.

John won Long Range pretty handily with the combination at least once. I don't believe Whidden makes choices without fully investigating his available options (which are ALL of the options).

 

[Ned Ludd]

As a general rule of thumb, it is always best to use the minimum amount of twist required to fully stabilize your bullet of choice under the particular atmospheric and elevation conditions you're shooting. In the OP's scenario, the 12-twist should be more than enough for lead core bullets in the 150-155 gr weight range.

However, there could be other factors involved that might affect the barrel twist rate choice, such as whether the OP might ever want to shoot longer (heavier) bullets in the future. In that event, I might actually choose the 10-twist as 155s will likely shoot reasonably well out of a 10-twist barrel, even though it's much faster than necessary. Bullets will generally tolerate being grossly overspun much better than they will being grossly underspun.

 

[Liven The Dream]

I have been at the Palma Game for years.
I have gone thru a few Barrels 30” and 32” .
With the Newer 155’s Sierras 2156 and Berger HB .
Times have changed .
We have a Barrel Maker that makes 1-12 Left Hand Twist ! Them flat work like a charm .
I won a Barrel from Broughton . I called them up to ask about how to order .
They recommend 1-11 5C .
I have this Barrel in 32” . It is a Velocity freak .
It take less powder to drive 155HB’s at my AV velocity . It also seems better at 1000 yards .

If you get a 1-10 Tight Bore ( .298X.365 ) ?
And go for HV Bullets Psi will be a Problem .
Kreiger has a Warning on His Web. site

 

[Park ranger]

Berger says BC will be comprised of twist is too slow yet stable. I’d go with 12

 

[FrankG]

I've shot 155's from Sierra and Lapua thru 1-12 twist on a palma gun, thru a 1-11.25 twist on my tactical bolt gun and 1-11 twist, 1-10 twist and a 18" 1-8 twist barrel. No issues on any of them accuracy wise.

That being said 168 AMAX box ammo I've shot thru the 11.25, 10 and 8 twist and again no issues.

My main go to bullets are the 155 Lapua's and 175smk.

You run the twist on the ragged edge and you get in different temp and climate and elevation conditions and you can run into problems stability wise and or give up some BC. I don't like running my stuff on the ragged edge and a little faster isn't going to hurt you like some think it will. In a really fast twist barrel maybe like a 1-8 and your shooting crappy bullets or your loaded ammo has a lot of run out in it then the really fast twist might have a negative effect on the accuracy.

Twist for the most part does not effect pressure. Same goes with left hand vs. right hand twist. You name the combination and we've probably made it. Even made barrels as fast as 1-1 twist in .30cal. That's not a typo! Yes 1-1 twist.

Once you start hitting twist of around 1-5 with box ammo and 175's bullet failure was pretty common. At that twist rate and say 2700fps the bullet comes out spinning at 388,800 rpm.

Bore and groove size will effect pressure. Groove size will have the biggest impact but anytime you change the total surface area of the bore you will effect the pressure curve. Just a recent test done by accident on three barrels where the bore and groove where .0005" undersize on each and it drove up the pressures 8k-10k psi.

Also what chamber spec. the reamer cuts the chamber at can effect pressures and velocities as well.

Unless you know the chamber spec. the guy is running and the bore and groove size of the barrel to the 4th decimal place you are not comparing apples to apples.

Later, Frank
Bartlein Barrels

 

[Paddyd]

I've shot 155's from Sierra and Lapua thru 1-12 twist on a palma gun, thru a 1-11.25 twist on my tactical bolt gun and 1-11 twist, 1-10 twist and a 18" 1-8 twist barrel. No issues on any of them accuracy wise.

That being said 168 AMAX box ammo I've shot thru the 11.25, 10 and 8 twist and again no issues.

My main go to bullets are the 155 Lapua's and 175smk.

You run the twist on the ragged edge and you get in different temp and climate and elevation conditions and you can run into problems stability wise and or give up some BC. I don't like running my stuff on the ragged edge and a little faster isn't going to hurt you like some think it will. In a really fast twist barrel maybe like a 1-8 and your shooting crappy bullets or your loaded ammo has a lot of run out in it then the really fast twist might have a negative effect on the accuracy.

Twist for the most part does not effect pressure. Same goes with left hand vs. right hand twist. You name the combination and we've probably made it. Even made barrels as fast as 1-1 twist in .30cal. That's not a typo! Yes 1-1 twist.

Once you start hitting twist of around 1-5 with box ammo and 175's bullet failure was pretty common. At that twist rate and say 2700fps the bullet comes out spinning at 388,800 rpm.

Bore and groove size will effect pressure. Groove size will have the biggest impact but anytime you change the total surface area of the bore you will effect the pressure curve. Just a recent test done by accident on three barrels where the bore and groove where .0005" undersize on each and it drove up the pressures 8k-10k psi.

Also what chamber spec. the reamer cuts the chamber at can effect pressures and velocities as well.

Unless you know the chamber spec. the guy is running and the bore and groove size of the barrel to the 4th decimal place you are not comparing apples to apples.

Later, Frank
Bartlein Barrels

Thanks everyone for the input. Currently I'm shooting an off the rack Savage 110 FP 308. I bought it in Minnesota sometime around 1994 for about $300? Since then I have put it in a cheap Choate varmint stock which really turned a very cheap rig into a real shooter. (At least it is when the barrel is squeaky clean) Today with Hornady brass on it's 3rd loading with 168 Amax's CCI standard primers and 46.5 gns of IMR 4350, it put 5 into 1/4" center to center @ 100 yds. It really does perform for what it is, but I have been hating the way it coppers up so fast and have been thinking of screwing a quality barrel on it. The reason I ask about the twist is that I have never had good luck with lighter bullets in this factory 1 in 10 barrel. 168 and the 175SMK's shoot as good as any custom rifle. I don't have a set bullet weight only as I'm just a hobby shooter and like to shoot whatever and experiment. All that said, it's sounding like maybe the 1/11 might help with the light varmint bullets, yet still be fine for the 175's. Am I in the ballpark or way off base in my thinking?

 

[FrankG]

Thanks everyone for the input. Currently I'm shooting an off the rack Savage 110 FP 308. I bought it in Minnesota sometime around 1994 for about $300? Since then I have put it in a cheap Choate varmint stock which really turned a very cheap rig into a real shooter. (At least it is when the barrel is squeaky clean) Today with Hornady brass on it's 3rd loading with 168 Amax's CCI standard primers and 46.5 gns of IMR 4350, it put 5 into 1/4" center to center @ 100 yds. It really does perform for what it is, but I have been hating the way it coppers up so fast and have been thinking of screwing a quality barrel on it. The reason I ask about the twist is that I have never had good luck with lighter bullets in this factory 1 in 10 barrel. 168 and the 175SMK's shoot as good as any custom rifle. I don't have a set bullet weight only as I'm just a hobby shooter and like to shoot whatever and experiment. All that said, it's sounding like maybe the 1/11 might help with the light varmint bullets, yet still be fine for the 175's. Am I in the ballpark or way off base in my thinking?

A 12 twist will handle up to conventional 190gr. bullets if memory serves me correctly. So pick your poison. 11 twist will work fine with no issues.

With it being a button barrel it could have a uniformity of twist problem. This usually makes them more temperamental as to what they like.

Copper fouling could be because how rough the bore is etc...