Twist rate 1:12 vs 1:10

Op I suggest you Take Ian's advice and go to a f-class shoot to see, a 20" barrel will not get you to 1000 very comfortably compared to longer barrels .
In my experience testing 308's the 185 gr bullets rule and a 10 twist is not needed for them a 1-12 will stabilize a 185 a lot use 1-11 .

20 or 24 " barrel is not a good choice for long range shooting @ 1000 I make barrels and the shortest I have made for long range is 28 normally 30 and a few 32 .
A 185 can be pushed above 2800 with a 30" barrel the pressures would be quite high in a short barrel to try and keep up.
 
Last edited:
coyote said:
Op I suggest you Take Ian's advice and go to a f-class shoot to see, a 20" barrel will not get you to 1000 very comfortably compared to longer barrels .
In my experience testing 308's the 185 gr bullets rule and a 10 twist is not needed for them a 1-12 will stabilize a 185 a lot use 1-11 .

20 or 24 " barrel is not a good choice for long range shooting @ 1000 I make barrels and the shortest I have made for long range is 28 normally 30 and a few 32 .
A 185 can be pushed above 2800 with a 30" barrel the pressures would be quite high in a short barrel to try and keep up.
Click to expand...

I will see when I can go to an F match. Maybe 20" barrel with 1:10 twist is good from short to mid-long distance then?

caramel said:
My FNAR is a 1 in 12 barrel and is extra precise with bullets rom 155 to 168 gr... JP.
Click to expand...

How accurate it is Caramel? What's the barrel length and how far you shot it?
 
Harry Callahan wrote "1:10 will stabilize longer (heavier) bullets, thus helping going the distance. 1:12 is too slow to properly stabilize heavier bullets. Tho some will say that 1:12 stabilize the 175's fine, I won't..."

There is an easy way to see if a bullet is stable. Shoot it at 100 yards. if it groups well, it is stable. As a bullet travels downrange it gains stability as it slows down (less air compression).

If you shoot at 100 and the group is big, or the holes are egg shaped, you need more twist, or more velocity or shorter bullets.

I have used a lot of 1:14 barrels on rifles intended to shoot milsurp 308. They shoot the Sierra 180 match just fine. Have not tried the 190s.

So, for those who want to shoot the 168 to 180 gr bullets, a 1:12 is more than enough.

A 1:10 is good for those who want to shoot the 200 gr VLD type bullets.

Over spinning bullets is not a good thing if you shoot mediocre bullets (milsurp) and not a good thing for long range (1000 yards and more). A bullet has gyroscopic stability. When you shoot a bullet at long range, it is aimed up, above the target. Down range the bullet slows and arcs down. Does the bullet tip over and aim down - or does it stay pointed up, because it is a gyro? If it stays pointed up, it comes down with a lot of side drag on the bullet.

The best twist is the twist that will just barely stabilize the bullet. Other than heavy VLDs, 1:12 is plenty. My 308s are all 1:14 and 1:13. I shoot 175 Sierra and 168 Amax as well as the various 155s.

My barrels run 30" to 32", and I get lots of velocity (more RPM). A shorter barrel needs a bit more twist. 1:12 is good.
 
Cpt.Flan said:
My 24" Bartlein 1-11 does wonders with the 168 and 175 .30cal bullets.

I want to try the heavier pills soon to experiment.
Click to expand...

Another vote for 1 in 11" twist......

I shoot a McPhee AMTU contour 26.5" 1 in 11.3" twist barrel using 178 gr. AMAX bullets. It will shoot 168 to 178 gr. very well.

For F-Class you will want a long barrel (28" to 32").

For Tactical or PRS style shooting a 26" barrel is plenty.
 
I love the FNH rifles, both my FNAR Competition ( 20 inch fluted )and my SPR308 ( 24 inch fluted) have the same quality barrel ( difference is lenght only ) in 1 in 12 ROT...
The FNAR'S are both sub MOA rifle with tailored ammo and the SPR is a .5 MOA rifle with quality handloads...
Personally, i would recomend the FNH products, even my FNH 45 Tac is an awesome pistol..JP.

006-6.jpg
[/URL][/IMG]
cXrAY8a.jpg
 
Best thing I ever did was to remove a 20inch 1-12 twist barrel and replace it with a 31inch 1-10 twist barrel.

At 1050 yards, the 175 SMKs were not even deformed after hitting the dirt (misses) in the 20inch. Now my 215 Hybrids hit with authority at the same distance with the 31inch tube.
 
There is more to twist than just stabilizing the bullet. It can affect performance.

Have a look at this article:
http://bulletin.accurateshooter.com...fficent-varies-with-twist-rate-stabilization/

The take-away is that BC drops off rapidly when SG is below 1.5

You will not be getting optimal performance out of many bullets with the 1-12. They may group well, but their ballistic performance will be degraded vs. firing them from a 1-10.

Try Berger's stability calculator, it tells you if BC is being compromised due to insufficient twist.
http://www.bergerbullets.com/twist-rate-calculator/
 
kombayotch said:
There is more to twist than just stabilizing the bullet. It can affect performance.

Have a look at this article:
http://bulletin.accurateshooter.com...fficent-varies-with-twist-rate-stabilization/

The take-away is that BC drops off rapidly when SG is below 1.5

You will not be getting optimal performance out of many bullets with the 1-12. They may group well, but their ballistic performance will be degraded vs. firing them from a 1-10.

Try Berger's stability calculator, it tells you if BC is being compromised due to insufficient twist.
http://www.bergerbullets.com/twist-rate-calculator/
Click to expand...

Thank for the readings Mod! It will benefit me.
 
Last edited:
Just an example: The 175 Match BT Long Range bullet fired at 2650 fps out of the 1-12 twist in std. conditions has a BC that is degraded by 6%. Pointing the bullet would maybe get you back to the unpointed BC of the bullet when fired out of the 1-10 twist.

Another reason why people's actual ballistics often don't match what the ballistics calculator is saying...
 
Anyone whos doing anything in f class out to 1000 yards is using the Berger 185 Juggernaut with 1:11 twist.
It's become the standard of the sport as of Aug 2015.

Just go with it and thank me later. If there was a better combo we'd be using it.

Just make sure you have a long enough throat on your chamber to keep the base of the bullet forward of the shoulder / donut on the case.
 
Sometime in the far future I will try to attempt to shoot 1000 yards and more with my 20" 1:10 FN SPR rifle. With the right bullet, is this possible?
 
BadAsMo said:
Anyone whos doing anything in f class out to 1000 yards is using the Berger 185 Juggernaut with 1:11 twist.
It's become the standard of the sport as of Aug 2015.

Just go with it and thank me later. If there was a better combo we'd be using it.

Just make sure you have a long enough throat on your chamber to keep the base of the bullet forward of the shoulder / donut on the case.
Click to expand...

For Team shooting, you are likely correct.

For individual... that debate still rages.

Jerry
 
You must log in or register to reply here.
Back
Top Bottom