Barrel twist vs length

Barrel twist vs length

This is a discussion on Barrel twist vs length within the Modern Sporting Rifles forums, part of the Sniping Related category; So I've read so many posts regarding bullet weight vs twist and so on. I guess my question or confusion come from twist vs length. ...

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Thread: Barrel twist vs length

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    Barrel twist vs length

    So I've read so many posts regarding bullet weight vs twist and so on. I guess my question or confusion come from twist vs length.

    Everyone else says for a .308 1:10 on a 20" barrel for a 165 grain

    Has anyone put a high twist on a long barrel? 1:6 1/8 1/9 1/10 on a 24, 26, 28 inch barrel

    How much an you squeeze? out of a .308 with say a 180 or 200 grain?

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    Senior Member deadshot2's Avatar
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    With barrel length comes speed (to a point). Bullets are stabilized by spin and as the speed increases, so does stability to a point. "Twist" is merely an indication of how far the bullet travels within a barrel before it turns one full rotation. That doesn't change because the barrel is long or short. If you increase the twist rate, you also increase the drag on a bullet as it passes down the barrel (from the force exerted at an angle to the direction of travel. Sometimes it's advantageous to decrease the twist rate and run a much longer barrel so you have the necessary speed to stabilize a bullet even though it's spinning slightly slower. It's not unusual to see shooters with 30" barrels and a 12 or 13 twist rate, looking for the high speeds to go long distances.

    As for a high twist on a long barrel, I have a very accurate .223 Bolt Action with a 1:7 twist and a 26" barrel. Shoots 80.5 gr Berger Fullbores with sub .25 MOA accuracy. As for .308, heaviest bullet for me is 1 178 gr A-Max from a 24" 1:10 barrel. I guess I could "squeeze" more out of heavier bullets but the 178's go as far as I need them to go, accurately.
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    Well I guess we're done here.

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    Super Moderator NorCalFocus's Avatar
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    Quote Originally Posted by Onemanmilitia View Post
    Everyone else says for a .308 1:10 on a 20" barrel for a 165 grain
    Define everyone else for me please. Because I've never heard that one. I know that lots of guys have shot 175-178 bullets out of 20" 1:10 barrels.


    To add to what deadshot already said, sometimes it also comes down to that barrel liking or not liking a piticular bullet and nothing else.
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    Senior Member ddd oo7's Avatar
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    180's stabilized just fine in my 22.5" 1:10 twist.

    I have heard of guys who used a 1:8 twist for 300wsm.

    I have a 1:7 in my 300 blackout and it stabilizes 220gr matchkings at subsonic speed.
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    Quote Originally Posted by deadshot2 View Post
    As for .308, heaviest bullet for me is 1 178 gr A-Max from a 24" 1:10 barrel. I guess I could "squeeze" more out of heavier bullets but the 178's go as far as I need them to go, accurately.
    Do you think it would be safe to get a 1:9? What kind of range are you shooting at?

    Quote Originally Posted by dddoo7 View Post
    180's stabilized just fine in my 22.5" 1:10 twist.

    I have heard of guys who used a 1:8 twist for 300wsm.

    I have a 1:7 in my 300 blackout and it stabilizes 220gr matchkings at subsonic speed.
    A 300wsm is more like a 338 Lapua correct? So much larger round... But a blackout is smaller then a 308..
    I realize the questions sound stupid.. I haven't had much experience in building a 308 so I'm having a barrel made and I only want to have to buy one... I've built lots of other ars just nothing that I've ever planed for long range.

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    Senior Member deadshot2's Avatar
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    Quote Originally Posted by Onemanmilitia View Post
    I haven't had much experience in building a 308 so I'm having a barrel made and I only want to have to buy one... I've built lots of other ars just nothing that I've ever planed for long range.
    Your gunsmith will be a great source of information on which caliber, barrel length, twist rate, and even reamer you should use. That is as long as you are using a gunsmith that has built a bunch of accurate LR rifles.

    Get on the phone and contact some of the well known barrel makers and gunsmiths that have been mentioned on this forum (like TS Customs, Mile High Rifles, Benchmark, Kreiger, Bartlein, etc) and ask them what they are seeing for the best (usually the most popular for them).

    A lot of decisions need to be made if you are going to do only one.

    FWIW, a lot of research was done with .308(7,62X51) when the M-24 SWS was developed. It was decided that for a 175 gr bullet in that caliber the optimal twist rate was 1:11.25" with a 5-R rifling configuration. The guys at Benchmark suggested 1:10 and I went with it. Never was disappointed.

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    if we stick with just 308 win/7.62x51 then there are lots of examples
    BUT
    first twist is related to bullet LENGTH, not weight.
    in palma 155 shooting 13 and 14 twist bbl were not uncommon
    if you only shot 165 a 12 twist would be fine. for a long time almost all
    308s came in 12.
    then came 175's and we moved to 10 for commercial guns but semi custom could see stuff in the 11 region.
    10 works for most up to 200.
    as usual decide what you want to do then build.

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    Senior Member deadshot2's Avatar
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    Quote Originally Posted by ar10ar15man View Post
    if we stick with just 308 win/7.62x51 then there are lots of examples
    BUT
    first twist is related to bullet LENGTH, not weight.
    in palma 155 shooting 13 and 14 twist bbl were not uncommon
    if you only shot 165 a 12 twist would be fine. for a long time almost all
    308s came in 12.
    then came 175's and we moved to 10 for commercial guns but semi custom could see stuff in the 11 region.
    10 works for most up to 200.
    as usual decide what you want to do then build.

    In some ways the prevalence of 12 twist rifle barrels in the civilian market made 1903 Springfields a favorite. A 10 twist with either 2 groove or 4 groove rifling was common. Also quite inexpensive. My
    Dad bought one in 1950 for a little over $12 and had it sporterized. I still have that rifle with it's original barrel and it shoots pretty nice for a "WWII Vet".

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    that would be a 30'06 not a 308...std twist on a 30'06.
    it was nice when new usgi bbl were under 100 bucks, but they have gone up a bunch.
    i have 2 03a3's.


    Quote Originally Posted by deadshot2 View Post
    In some ways the prevalence of 12 twist rifle barrels in the civilian market made 1903 Springfields a favorite. A 10 twist with either 2 groove or 4 groove rifling was common. Also quite inexpensive. My
    Dad bought one in 1950 for a little over $12 and had it sporterized. I still have that rifle with it's original barrel and it shoots pretty nice for a "WWII Vet".

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