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Thread: 1/7 vs 1/8 barrel twist

  1. #1
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    1/7 vs 1/8 barrel twist

    Hi,

    I want to put together a mk 12 spr rifle. I know that the 1/7 is the correct mil spec twist rate, but the uppers with that rate are currently backordered. As a practical matter, how much of a difference would it make to go with a 1/8 twist Douglas barrel? To be honest, I don't know how much mk 262 77 grain ammo I'll be shooting due to cost. I'll probably be using a fair amount of 55 grain range ammo. How much worse would the performance be?

    thanks.

  2. #2
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    1/8 twist is a good all round twist rate. I've fired some decent scores at 200 yards with a 1/8 twist barrel and PMC 55g FMJ. The Junior High Power Team in our area shoots with 1/8 twist barrels at Camp Perry every year and they do quite well.
    Train 2 Win

  3. #3
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    If it'll fit in a magazine, 1/8 will stabilize it.

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    Quote Originally Posted by 17K View Post
    If it'll fit in a magazine, 1/8 will stabilize it.
    And then some. 1/8 barrels stabilize my 600 yard loads, which are too long for a magazine and have to be loaded one at a time.
    Train 2 Win

  5. #5
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    Quote Originally Posted by cropsey View Post
    As a practical matter, how much of a difference would it make to go with a 1/8 twist Douglas barrel?
    Not a damn thing, worry more about the reputation of the barrel maker than the twist rate.
    Last edited by vicious_cb; 06-30-20 at 01:06.

  6. #6
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    1:8 works fine with my 20” SPR build and 75gr OTM, 70gr GMX, and 73gr ELD bullets loaded to magazine length.


    Andrew - Lancaster, CA
    NRA Life Member, CRPA member, Calguns.net contributor, CGF / SAF / FPC / CCRKBA / GOA / NAGR / NRA-ILA contributor, USCCA member - Support your defenders!

  7. #7
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    Quote Originally Posted by T2C View Post
    And then some. 1/8 barrels stabilize my 600 yard loads, which are too long for a magazine and have to be loaded one at a time.
    80 SMK or 75 ELD? I'm curious. What barrel length also?

  8. #8
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    Quote Originally Posted by FightinQ View Post
    80 SMK or 75 ELD? I'm curious. What barrel length also?
    80g SMK shot out of a 20" barrel.
    Train 2 Win

  9. #9
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    Quote Originally Posted by 17K View Post
    If it'll fit in a magazine, 1/8 will stabilize it.
    This has been my experience, as well. However, given the choice, I prefer 1/7. I launch long bullets through short barrels and suppressors, so it just makes me feel better. But, I’ve had no issues with 1/8, even with long copper bullets.
    RLTW
    “Yep, it's definite. I simply don't care enough what you think.” -SteyrAug

  10. #10
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    Quote Originally Posted by T2C View Post
    80g SMK shot out of a 20" barrel.
    We run those on occasion out of a 1/9 nominal, 20" barrel with no issues. Unless the OP is shooting M856 tracer in a short barrel, 1/8 is plenty of twist.
    "You people have too much time on your hands." - scottryan

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