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Thread: 1/7 or 1/9 barrell twist..???

  1. #1
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    1/7 or 1/9 barrell twist..???

    Is there a signifigant difference between 1/7 and 1/9 twist? And if so what is the effect, and should a AR novice really care? I'm sure this has been question has been beaten to death on this forum so thanks for the info in advance.......

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    If you want to shoot anything over 69 grains get a 1/7. I have no need for that so most of my barrels are 1/9.

    I run a few 1/7s but that is only because some barrels only come in that twist.
    "You people have too much time on your hands." - scottryan

  3. #3
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    Quote Originally Posted by moresky View Post
    Is there a signifigant difference between 1/7 and 1/9 twist?
    That depends on wat you consider significant. The 1/7" twist will handle the heavier bullet weights.


    Quote Originally Posted by moresky View Post
    And if so what is the effect
    If the twist is too slow for the load, you'll get key-holing, i.e. the bullet will start to tumble during it's trajectory.

    Quote Originally Posted by moresky View Post
    should a AR novice really care?
    Probably not. The AR novice in all likelihood would be sticking to 55grn and 62grn rnds that the 1/9"can handle

    Quote Originally Posted by moresky View Post
    I'm sure this has been question has been beaten to death on this forum so thanks for the info in advance
    Not sure if it's been beaten to death here but it has elsewhere

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    Just to add, I regularly shoot 75-grain Match ammo (Black Hills) out of my Bushy Varminter which has a 1/9 twist barrel. I have hit a 10-inch plate with this out to 926-yards and if I were to do my part (which is very rare), it would put the round after round into the same hole at 100-yards. FWIW.
    We must not believe the Evil One when he tells us that there is nothing we can do in the face of violence, injustice and sin. - Pope Francis I

  5. #5
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    If you have the choice ,get a 1/7. 75 and 77 grain preform well with a 1/7 twist .the Hornady 75 tap and the 77 SMK rounds are the trend for SD and a lot of PD's use the .556 Hornady tap as thier day to day ammo . get the 1/7 use 75 and 77 grain ammo ,better range,and better stopping power .
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    thanks for th replies.....good info........

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    I just sold my upper and built another just for a 1/7" twist barrel.

    Both will shoot 55gr. ammo just fine.

    Some 1/9" will shoot the latest/greatest 77gr. defensive ammo, but some don't.

    I wanted the 1/7" so I could shoot 77gr.

    Plus, most of the 4150 CMV barrels out there only come in 1/7" twist

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    I like the 1/7 good use for all types of ammo.I stay as close to Military spec as I can with my cilvilian rifle.just with out the go-fast switch .you can put all types of optics but unless that barrel is set up for the ammo you use ,you will not get the best out of either.there is a list somewhere that compares the twist rates with differant ammo but I don't have a clue to find it


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  9. #9
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    I personally have no use for a 1/9 barrel.

    1/7 does just fine with most 45gr bullets (if you decide to vaporize a few groundhogs) and will definately work with the optimumly performing 77gr bullets (where the 1/9s are hit and miss if they will work with the longer bullets).

    Of course, if you only intend on shooting 55gr(-) bullets, the 1/9 is going to work fine.

    Some reading for you:
    1/7 Twist and 55gr Rounds
    1 in 9 twist with TAP 75 gr
    barrel and twist vs bullet

    Take the time to read these threads.
    Jack Leuba
    Military/Government Product Liaison
    Knight's Armament Company
    jleuba@knightarmco.com

    Director of Training

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    Quote Originally Posted by Failure2Stop View Post
    I personally have no use for a 1/9 barrel.

    1/7 does just fine with most 45gr bullets (if you decide to vaporize a few groundhogs) and will definately work with the optimumly performing 77gr bullets (where the 1/9s are hit and miss if they will work with the longer bullets).

    Of course, if you only intend on shooting 55gr(-) bullets, the 1/9 is going to work fine.

    Some reading for you:
    1/7 Twist and 55gr Rounds
    1 in 9 twist with TAP 75 gr
    barrel and twist vs bullet

    Take the time to read these threads.
    outstanding thanks for the links.


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