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Discussion in 'Rifle Discussion' started by Barefoot343, Sep 16, 2011.

  1. Barefoot343

    Barefoot343 liberalville Active Member

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    when looking at AR's can somebody explain the difference between a 1/6 twist and 1/9 twist on a barrel? I understand the twist itself and the purpose, just don't know what the numbers represent, which is better and why? and what is the number refering to?

    Thank you.
     
  2. saxon

    saxon springfield Active Member

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    1/6 1 full rotation in 6 inch's 1/9 1 full rotation in 9 inch's and then the old 1/12 1 full rotation in 12 inch's
    Early models had a 1:14 rate of twist for the original 55 grain (3.6 g) bullets. This was changed to 1:12 when it was found that 1:14 was insufficient to stabilize a bullet when fired in cold weather. Most recent rifles have a 1:9 or 1:7 twist rate. There is much controversy and speculation as to how differing twist rates affect ballistics and terminal performance with varying loads, but heavier projectiles tend to perform better with faster rifling rates.[15] Additionally, the various non .223 / 5.56 calibers have their own particular twist rate, such as 1:10, 1/11 and 1/12 for 6.8x43mm SPC, 1/10 7.62x39mm, and 1:12 for .308 Winchester
     
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  3. wayoutwest

    wayoutwest Polk County, Oregon Active Member

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    1/6.....1/7...1/9....1/12...etc...the number of revolutions the bullet makes in an inch. The faster the twist rate the faster it will stabilize.

    Which is better and why depends on the caliber/barrel length/bullet weight etc

    1/7 is good for 62grain and up
    1/9 is a very typical twist and will turn a 55 grain bullet well
    1/12 is slower and will turn lighter grain bullets
     
  4. Barefoot343

    Barefoot343 liberalville Active Member

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    good info,

    so would you say the more revolutions a bullet makes the less distance it may travel due to friction? (I am in a physics class this term) which it sounds like you are explaining Saxon. At the end of the day which is a better twist for a common AR a 1/6 or 1/9? 1/9 is more common right?
     
  5. saxon

    saxon springfield Active Member

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    wellll,,,,,,,,,,,,,,,,,,, you are talking apples and orange's the twist will also depend on what grain bullet you use,
    so more like a fruit salad you need to know what you want to do and what your going to use to do it
     
  6. Barefoot343

    Barefoot343 liberalville Active Member

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    ok, thats what I figured. Curious what twist the military uses since there are so many uses (close combat, farther shots 100 yds -500yds range it would seem)

    Anyway thanks for the info.
     
  7. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    OK saxon has taken care of the smart stuff. All I can add is both of my ARs have a 1-8 twist and I have shot every grain I could find through them with no negligible difference in accuracy. (55grain thru 78 grain)

    So I would say go with the "in between" twist at 1 in 8
     
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  8. saxon

    saxon springfield Active Member

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    lol yes but i grew up and went back to a real mans man of a cartrige :D back to 30-06 and 7.62X54 and 7.62X39 lol
     
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  9. mjbskwim

    mjbskwim Salmon,Idaho Well-Known Member

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    Oh,those are in the works. I have the X54 and one SKS,so I'm ether going for the X39 or the X51 with the AK in the lead because of ammo prices.
     
  10. 22many

    22many PNW Well-Known Member

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    If what you are getting at is buying a ar in another caliber other than 5.56 I doubt your gonna find a big selection on twist rates. My ar in 7.62x39 has a 1 in 12 twist and I think the only other option is maybe a 1 in 10. The 6.5, 6.8, 9mm, ect, ect, wouldn't surprise me if they offered only one option.
     
  11. madcratebuilder

    madcratebuilder Ardenwald, OR Well-Known Member

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    :huh::huh:NO!:huh::huh:

    "the number of revolutions the bullet makes in an inch"

    The bullet would disintegrate at those rotational speeds.


    Try the number of inches the bullet travels in one revolution. :thumbup:

    twist rates are approximate and can vary as much as a half inch.
     
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  12. iamme

    iamme Lane County Well-Known Member

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    223/5.56 "standard" is 1/7. 1/8 is a great tradeoff to run different ammo with. Like others have said once you get to other platforms you'll probably see less options- Unless talking bolt guns, etc.
     
  13. saxon

    saxon springfield Active Member

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    i meant that i moved on from the evil black rifle :D back to guns that will kill what you shoot out to 1,000 yards