What twist?

[Dragoon300]

I am hooked on Bartlein's Transitional (gain) twist barrels, with 5R lefthand rotation rifling. Take the twist rate you want, and start 1 revolution slower, transitioning faster to the muzzle, ending at the rate you desire. I have a 6.5 PRC with 1:8.5 to 1:7.5 5R LH that is working great. The gain twist is easier getting the projectile up to speed, especially good for fast twist rates, less starting pressure, and continues to seal better all the way to the muzzle. The 5R rifling is easier on the jackets, and lefthand rotation helps decrease coriolis effect in the Northern hemisphere. I have also done this with great success on my 338 Lapua. In fact I just read Frank Galli's book on precision rifle where he is suggesting this same thing. It really is worth it!

 

[Paulstarr]

1in 9 is ample for stability,25-06 is a bit of a throat burner anyway, so going tighter won't help.I used to own one,a Remington 40X great rifle.1in 9 will easily handle 120gn bullets.

 

[Rhino Hunter]

Your example is incorrect.
For a given twist rate when you increase velocity you increase stability.
Example, shooting a xx grain bullet through a 16 inch barrel is less stable than the same bullet being shot through a 20 inch barrel because of increased velocity.

I was confused when I read this also, and couldn't understand how this could be.

 

[Paulstarr]

PDR / Parabolic Drag Reduction
SF / Stability Factor
TSF / Terminal Stability Factor

Butterbean,they are just posh words for the same thing.Bullet manufacturers invent their own names for very low drag,I'm like you,I have to look it up.

 

[Orange Dust]

1in 9 is ample for stability,25-06 is a bit of a throat burner anyway, so going tighter won't help.I used to own one,a Remington 40X great rifle.1in 9 will easily handle 120gn bullets.

Not unleaded

 

[Eric H]

I've just recently started using WWW.bisonballistics.com and using the Stability Calculator. Take a look and remember you're looking for a number between 1.5 and 1.7. It seemed to work for me in loading for the 6MM ARC.

 

[sodakota]

There's on-line calculations for determining whether or not a bullet will be stabile, Berger has one of those sites. Once the bullet is stabile I do not see any advantage of a faster twist.
There's lots of items that affect the stabilization. Such as atmospheric press, humidity besides bullet shape and length.
I have a fast twist 280AI (premium barrel) and a standard 700 in 7mm RM.
One odd thing is the 7mm RM easily shoots ABLR bullets better than the 280AI. That 280AI shoots bug hole groups with many bullets though.
go figure

 

[Al Arseneault]

I need a twist recommendation for a 25-06 to be able to stabilize the hammer 116 grain and/or the 121 grain hammer hunters. The 1-10 twist that my Winchester 70 isn't doing it. At a hundred yards, accuracy is not good at best, and just not acceptable. Thanks

 

[ButterBean]

There's on-line calculations for determining whether or not a bullet will be stabile, Berger has one of those sites. Once the bullet is stabile I do not see any advantage of a faster twist.
There's lots of items that affect the stabilization. Such as atmospheric press, humidity besides bullet shape and length.
I have a fast twist 280AI (premium barrel) and a standard 700 in 7mm RM.
One odd thing is the 7mm RM easily shoots ABLR bullets better than the 280AI. That 280AI shoots bug hole groups with many bullets though.
go figure

Simple way to look at it, A drill bit, 10 Twist=2.4 turns per 24', Slow Drill Bit 7 Twist= 3.4 turns per 24', Fast Drill bit / Avg Deer is 24' thick, Do you want your bullet to spin 2.4 times inside the deer or 3.4 times ?

 

[Al Arseneault]

I need a twist recommendation for a 25-06 to be able to stabilize the hammer 116 grain and/or the 121 grain hammer hunters. The 1-10 twist that my Winchester 70 isn't doing it. At a hundred yards, accuracy is not good at best, and just not acceptable. Thanks

Keep the 25-06 for lighter fast bullets and but a 270 Winchester to shoot a little heavier ones. You can probably pick one up for a little more than replacing a barrel than may not shoot very well.

 

[PatriotHenry]

I need a twist recommendation for a 25-06 to be able to stabilize the hammer 116 grain and/or the 121 grain hammer hunters. The 1-10 twist that my Winchester 70 isn't doing it. At a hundred yards, accuracy is not good at best, and just not acceptable. Thanks

I would call Hammer Bullets. You get the Owner on the phone and he will help you. Very rare to get that kind of service nowadays.

Good luck with your project!

 

[RCMSTER]

Keep the 25-06 for lighter fast bullets and but a 270 Winchester to shoot a little heavier ones. You can probably pick one up for a little more than replacing a barrel than may not shoot very well.

I already have a 6.5-06, 1-8 twist Brux barrel. It shoots really well, considering the nut behind the trigger gets loose once in a while, although I haven't tried hammer bullets in it. The previous owner was shooting .3", 3 shot groups with it @ 300 yards, and I know for a fact I couldn't shoot like that.

 

[Eric H]

BISONBALLISTICS.COM shows the 116 gr stable in 1/9 twist and not the 121. Once calculating, the site show what to expect in the next faster and slower twists.

 

[RCMSTER]

BISONBALLISTICS.COM shows the 116 gr stable in 1/9 twist and not the 121. Once calculating, the site show what to expect in the next faster and slower twists.

Well, I'm pretty sure the 116 isn't stable in my 1-10 twist. Either that, or I'm alot worse shot than I thought I was. And so from what you're telling me, is that I should go with a 1-8 twist perhaps, or maybe a 1-7.5 twist?