What is the best rifle twist?


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Plank Road Farm
December 21, 2011, 05:07 PM
I am thinking about ordering a 6.5x55mm Savage drop in barrel.
I need to know what twist to select.

Which would you choose & why?

The vendor choices are:

6.5 cal 1-8" 6 Groove 130 Grain or heavier
6.5 cal 1-8.5" 6 Groove 130 Grain or heavier
6.5 cal 1-9" 6 Groove Up to 130 grain bullets
6.5 cal 1-10" 6 Groove Up to 125 grain bullets

I am leaning towards 1:8, not sure.

I want a twist that allows for the most range of bullets & accuracy.

Will be used to hunt coyote to deer.

TIA

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rcmodel
December 21, 2011, 05:31 PM
The original Swedish Mauser used approximately a 1/7.8" twist.

It will handle 100 Spitzer to 160 grain round nose.

rc

Strykervet
December 21, 2011, 06:04 PM
This is what I use when I order barrels. This is from Wikipedia:


"Twist = (CD^2)/L X Sqrt.(SG/10.9)

where:
C = 150 (use 180 for muzzle velocities higher than 2,800 f/s)
D = bullet's diameter in inches
L = bullet's length in inches
SG = bullet's specific gravity (10.9 for lead-core bullets, which cancels out the second half of the equation)"

For those that don't know the "symbols" used in expressing math on the computer, "Sqrt." is "square root", so the square root of that expression, and "^2" means "squared", so D is squared, multiply it by itself.

Like the variable definitions say for SG, unless you are using Barnes bullets, that whole term goes away and you don't need to take the root of anything. The equation for regular lead core bullets like SMK's and most everything else but Barnes bullets is:

Twist = (CD^2)/L

When I order I optimize the twist rate for the bullet weight I intend on using the most. The other weights will work too, but you'll theoretically get the highest performance or optimization possible with regards to the twist rate for at least the one specific bullet weight you intend on using most.

redbullitt
December 21, 2011, 08:50 PM
i have a 260 rem screwed on a savage action and the 8 twist works great for me. I shoot 142 smk and the 140 smks. both shoot great.

Big20
December 23, 2011, 01:17 PM
Take it from a Remington Mdl 7 owner with the old, 1 in 10 twist. It WILL NOT shoot anything over 120 grains.

snakeman
December 23, 2011, 01:45 PM
I would go with a 1:8. That's what most ammo was designed for and it should shoot most of it just fine.

USSR
December 23, 2011, 02:28 PM
I use the 139 - 142gr match bullets exclusively. I had my 6.5x55 match rifle built with a 1-8.5" Obermeyer barrel. I would recommend that twist first, and a 1 - 8" twist second.

Don

Float Pilot
December 23, 2011, 07:22 PM
The bullet length and not the weight is the prime factor when deciding on a rifling twist.
The original Swede Mauser twist rate was 1 in 200mm. The CG-63 target rifles which were built around a 139-140 grain boat-tail had a 1 in 220mm twist rate. Although some had Schultz and Larsen barrels with a 1 in 9 inch rate. (I have one of those)

My old military Swede's and my M-70 Winchester will stabilize very long bullets. The CG-63 with the 1 in 9 twist and my Sako with a 1 in 9 twist will only stabilize the shorter bullets.

Go with the tightest twist listed..

browningguy
December 23, 2011, 10:48 PM
I like the 8 twist, no question they will stabilize the heaviest bullets.

Matthew Courtney
December 24, 2011, 04:54 PM
For hunting with heavy bullets 1/8.5
For long range targets 1/8

If there was a best twist, they wouldn't make more than one. A lot of folks overstabilize bullets, which leads to poor terminal performance. An overstabilized bullet will keep its nose pointed in the direction of initial travel when its travel direction turns downward. This can result in a bullet hitting ogive first instead of point first. Bullets hitting that way will not expand on game as designed, but they do make a larger hole in a target, which increases the chances of breaking a higher scoring ring.

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