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Old May 9, 2013, 01:58 AM   #1
Scottish Highlander
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Barrel twist question

Hi everyone, as a few know I have a 308 Tikka t3 hunter as my primary rifle. It as far as I believe has a 1/11 twist. I know you can get different barrels with different twists built into them. I've read that different weight bullets react better to different twist ratios. I'm just heading out to work for a 10 hour shift so wont be back for a good while but my question was what is the difference and what benefits do they offer. I'm in the middle of testing a Hornady 168 grain A-max just now and getting ok performance with IMR 3031 but I am planning buying some R15 next due to a lot of good reports on here about it. The bullets I'm testing are for reaching out to 600 yards or more with good accuracy results hopefully .

Hunting season for red stags will be here soon to so any suggestions of a good Hornady hunting bullet would be much appreciated to for the R15 powder.

Thanks Guys and Galls , hope you have a good day

Jamie
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Old May 9, 2013, 03:26 AM   #2
Bake
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Slower twist rates will work better with lighter bullets, and the faster twists will work better with heavy bullets.

My guest, is your 11:1 will work with bullets between 150 & 168 grains. The 10:1 will work with 160 to 180, or maybe 190 grains. The 9:1 will require a 190, up to 210 or 220.
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Old May 9, 2013, 03:41 AM   #3
darkgael
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Twist

With all due respect, the relationship between a bullet and the proper twist rate has little to do with bullet weight.
The Greenhill Formula for calculating twist rates does not require any weight input, though there is input for specific gravity. The necessaries are bullet length, bullet diameter, and velocity.
See this link:
http://kwk.us/twist.html

Pete
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Old May 9, 2013, 07:22 AM   #4
Bart B.
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That Greenhill formula originated in the late 1800's. C.E. Harris, writing in the 08/1983 issue of the American Rifleman, noted Greenhill's formula was developed before spitzer boattail bullets and high velocity cartridges. He used a more modern analysis of gyroscopic stability, in which a factor of 1.4 is minimum and 1.7 is usually good. He found that the numbers given by Greenhill's original formula ranged from 1.5 to 2.0 for military type boattail bullets and were about 2.0 for bullets with either a flat base or short boattails.

While oft times claimed to be "the" standard for calculating twist rates for bullets, the Greenhill formula's been superceded by more accurate methods. For example, Sierra Bullets uses the time of flight between two points testing their bullets, The twist that ends up with the lowest spread in time of flight for a given bullet best balances it so its drag (ballistic coefficient) numbers have the lowest spread.

For decades, those "in the know" (competitve shooters producing the best results) have used the slowest twist that stabilizes bullets all the way to the target. The following twist rates for the 308 Win. cartridge shooting spitzer bullets of different weights leaving at typical muzzle velocities:

240 grain, 1:8
220 grain, 1:9
200 grain, 1:10
185 & 190 grain, 1:11
168, 175 & 180 grain, 1:12
150 & 155 grain (short barrels and ranges), 1:12
150 & 155 grain (long barrels and ranges), 1:13
135 grain, 1:14

For a wide range of bullet weights, it's best to use the twist that best stabilizes the heaviest bullet used. Which is why factory sporter barrels have the twists used; 1:10 for a .30-06, for example as it will handle bullets up to 220 grains quite well and lighter ones at 150 grains will still perform good enough for general use.
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Last edited by Bart B.; May 9, 2013 at 07:28 AM.
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Old May 9, 2013, 07:47 AM   #5
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Bart,

Really like your detailed posts. You help a lot of us better understand why we see the things we do. Thanks for taking the time to elaborate.
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Old May 9, 2013, 11:38 AM   #6
Scottish Highlander
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Bart,

Thanks for your detailed post. Its funny how I've always been told to use 125 - 130 grain loads for my rifle. By the sounds of it I'd be far better to use a heavier bullet to suit the 11-1 twist. As I previously mentioned I was working on a load with the Hornady A-max 168 grain. From what your saying maybe I'd be better to jump another 10 grains up in bullet weight and see how things pan out from there....

I think for the game load I'll stick with the 150 grain load that I've settled on.

Thanks again
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Old May 9, 2013, 12:55 PM   #7
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Quote:
I think for the game load I'll stick with the 150 grain load that I've settled on.
If your rifle will shoot them accurately that is what I would do also. I have a Remington 700P in .308. That rifle will not shoot 150/155 grain bullets worth a hoot. I have tried all sorts of load variations and my gun just does not like them. Switch to 168 gr, Federal trophy loads or hand loads with 165/175 bullets and the gun just comes alive. My M1A on the other hand shoots the 145/146/147 milsurp just fine as well as the Federal 168 gr. loads. It is funny that rifles are sometimes so picky that way.
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Old May 9, 2013, 07:58 PM   #8
darkgael
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Twist

Bart: Always great info.
Quote:
150 & 155 grain (long barrels and ranges), 1:13
Is that the norm for Palma rifles?
Pete
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Old May 9, 2013, 08:09 PM   #9
Bart B.
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Pete: yup, 30 inch long Palma barrels typically use a 1:13 twist. My first Palma barrel had a 1:12.7 twist, two of the other three had 1:13 twists and one had a 1:12 twist.

I think a couple of Brits from England had 1:14 twists in their Palma barrels when Sierra's 155's were first used in a match back in 1991. They shot those bullets very well at 6600 feet elevation where the air's thin and they could get away with a slower twist.
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Old May 10, 2013, 12:07 AM   #10
hoghunting
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Quote:
Hi everyone, as a few know I have a 308 Tikka t3 hunter as my primary rifle. It as far as I believe has a 1/11 twist.
Are you sure it's a 1/11 twist as their .30 caliber barrels were the standard 1/10 twist?
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Old May 10, 2013, 01:40 AM   #11
Scottish Highlander
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Hi Hoghunting,

I checked the web site and looked at the tikka t3 hunter and it stated there it was a 1-11 twist in black and white. Unless I'm mistaken or proven wrong then it is as it stated. I suppose I could call them with the serial number to find out but I dont think I really need to

Jamie
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Old May 10, 2013, 08:22 AM   #12
JD0x0
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According to Berger...

You can go up to 210 gr VLD with a length of 1.459'' with 1:11 twist
and up to 230 grain VLD with a length of 1.64'' with 1:10 twist
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Old May 10, 2013, 06:59 PM   #13
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Quote:
With all due respect, the relationship between a bullet and the proper twist rate has little to do with bullet weight.
The Greenhill Formula for calculating twist rates does not require any weight input, though there is input for specific gravity.
Yes, but bullet length and bullet weight go hand in hand. In order to make a bullet heavier, you have to make it longer, so twist rates coupled to bullet weight is a pretty good rule of thumb, if not perfect.
If you are casting bullets out of aluminum or 24K gold instead of lead, this does not apply.
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Old May 10, 2013, 11:45 PM   #14
hoghunting
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Quote:
I checked the web site and looked at the tikka t3 hunter and it stated there it was a 1-11 twist in black and white. Unless I'm mistaken or proven wrong then it is as it stated. I suppose I could call them with the serial number to find out but I dont think I really need to
You don't have to call them, you can check it yourself with a cleaning rod and either a brush or jag.
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