1:7 twist vs. 1:9 twist

Discussion in 'The Powder Keg' started by 1BigPig, Aug 5, 2008.

  1. 1BigPig

    1BigPig G&G Newbie

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    Can someone explain to me the positives/negatives or advantages/disadvantages and differences between 1:9 twist barrels and 1:7 twist barrels? It seems like with most brands the 1:7 twist is an upgrade.
  2. GlockMeister

    GlockMeister G&G Enthusiast

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    I'm no expert, but here's what I know. The 1:7 twist can stabilize heavier bullets more so then the 1:9 twist rate. The 1:9 is the most common of the 2 when it comes to factory builds and for the most part, custom and home builds as well. The 1:7 is a choice for many home and custom builds as well though. 1:7 twist has it advantages over 1:9 which is why it's considered an upgrade from the 1:9.
    I'm sure there's more to it then this, but that's what I've picked up on it. Hope it helps even a little.
    Last edited: Aug 5, 2008
  3. wunhunglo

    wunhunglo G&G Newbie

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    The heavier bullets only really come into their own at longer ranges. If you're not going to be shooting at over 300 yards and unless you're getting into competitive shooting, a 1 in 9 will probably be all you'll need. I'm a middle of the road guy so I got a 1 in 8 and shoot 75-80 gn bullets at up to 600m. Would a 1 in 7 be better for me?? I don't know, but on a good day I can put all the rounds in the x-ring at 600m with what I've got.
  4. GlockMeister

    GlockMeister G&G Enthusiast

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    Hey wun, is then 75gr too much for a 1:9 twist? If so, what about 69gr.?
  5. wunhunglo

    wunhunglo G&G Newbie

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    I'm no expert but I believe that the 62-69 grain bullets are supposed to give the best performance in the 1 in 9 twist. I think that the 75 is too heavy to be properly stabilised in it. I do know that my 20", 1 in 8 gives fairly good performance with the 62gn RG SS109 up to about 3-400 metres and excellent performance with 75 & 80 gns up to 600. Actually it's a tie between the 75 gn Hornady & the 80gn sierra but I've never managed to get hold of enough 77gn Sierra to try yet.

    EDIT: For info, in the UK, SS109 surplus ammo is much more common (nato spec) than the 55gn stuff so we tend to prefer the slightly faster twist rate.
    Last edited: Aug 5, 2008
  6. GlockMeister

    GlockMeister G&G Enthusiast

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    Thanks.

    And 1BigPig, FWIW, go with 1:9. Unless you plan on doing most of your shooting as wun stated.
  7. at4rxj

    at4rxj G&G Newbie

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    If you can get it for the same price, get the 1:7. You (theoretically) cannot "overstabilize" a bullet. The 1:7 will shoot the 69gr and heavier bullets, while the 1:9 will only shoot up to the 69gr reliably, and sometimes not even that. I prefer the 1:7 for that reason alone.

    There are people that have 1:9 barrels that shoot 75gr bullets, but this varies per rifle. If it's a huge price difference, and you don't plan on shooting the 75gr bullets at all, then don't sweat it. If it's the same price, or even a little more, I would personally say to go for the 1:7.

    Just my thoughts....
  8. connormcmanus

    connormcmanus G&G Newbie

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    So I'll just go ahead and assume that 1:10 would be ludicrous, yes?
  9. at4rxj

    at4rxj G&G Newbie

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    No, you'll just be limited to lighter bullets
  10. 1BigPig

    1BigPig G&G Newbie

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    I know it's not reccommended to shoot a .223/5.56 deer hunting, but if I were going to try to deer hunt with it, I would want to shoot the heaviest bullet I could find. Would any performance be lost shooting the lighter bullets in the 1:7? Thanks for all the input!
  11. oejeffrey

    oejeffrey G&G Newbie

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    I shoot a krieger barreled Bushy with a 1:7 twist, 20 inch free floated. For fun I go shoot sierra 69 grain HPBT. For competion I shoot the 77 grain HPBT sierras. Do the 8 grains make a difference? You bet they do...in my head !!!
  12. 1BigPig

    1BigPig G&G Newbie

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    Hey At4rxj, I do want to shoot heavier bullets, albeit probably much less than 300 yards. Also, does barrel length come into play because I really want to stick with a 16" barrell. JT Distributing has a chrome lined 16" barrell with 1:7 twist.
  13. at4rxj

    at4rxj G&G Newbie

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    Barrel length does come into play, but to my understanding, with a shorter barrel you want a faster twist like 1:7 or 1:8.

    You shouldn't see any adverse effects shooting lighter bullets in a 1:7 barrel. If you get down to extremes you may, but typically you see 50-75gr bullets, and the 1:7 would handle those perfectly.

    The barrel you name above sounds perfect. Do you have a link to it?
  14. 1BigPig

    1BigPig G&G Newbie

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    J&T 16" DS-4 CAR Kit The last option is Barrel and they have a 1:7 Twist Gov't Profile Chrome lined barrel for a $50 upcharge.
  15. at4rxj

    at4rxj G&G Newbie

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    Yeah, I see it. That's a good deal. You're paying the $50 for the chrome lining, though, not the 1:7 twist (they also have a 1:7 non chrome lined with no up-charge)

    I'd go with the 1:7. You won't see any difference shooting the lighter bullets... The chrome lined part is up to you. Personal preference in my opinion.
  16. Reckt88

    Reckt88 G&G Newbie

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    Since the 1:7 doesn't have any problems shooting the lighter bullets, why does anyone even buy the 1:9?
  17. ClayMan

    ClayMan G&G Regular

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    Here's another variable that can come into play as far as which bullet weights a particular gun will shoot well: leade or freebore. As I understand it, this is the amount of space in the front of the chamber (where the bullet is inserted) that is not rifled.

    From what I understand, there are differences between a true .223 Winchester chamber and the 5.56x45 NATO chamber. And, the "Match" designation may indicate that there is a slightly longer leade (or freebore) to allow heavier and longer bullets to chamber without contacting the rifling.

    In my particular experience, I have a Colt Match HBAR chambered in 5.56x45 NATO, 1:7 twist rate, 20" length. If I stick with 62 grain or heavier bullets, I get great accuracy. But, if I shoot 55 grain bullets, my group sizes increase by several inches.

    So in my case, I really don't know if:

    1) the faster twist rate cause the lighter bullets to "overstabilize"

    2) the "Match" designation means I have a longer leade causing the shorter 55 grain bullets to wobble before engaging the rifling which affects accuracy

    3) or some combination of the 2 above

    What I do know absolutley, from extensive testing/shooting with all kinds of factory loads, is that with my gun I must stick with 62 grain or heavier bullets. If I shoot 55 grain bullets, I get poor/frustrating groups even at short ranges of 50 yards.

    ClayMan
    Last edited: Feb 14, 2009
  18. SwedeSteve

    SwedeSteve Freedom Zealot Forum Contributor

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    Great discussion, thanks guys !!
  19. NRAJOE

    NRAJOE YOU TALKIN' TO ME!? Forum Contributor

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    1:9 is the better overall twist...can shoot just about anything with decent accuracy.
  20. Johnnycat

    Johnnycat G&G Newbie

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    To me this is the post/question of the day. I would love to hear more opinions.

    It has been my understanding that too fast spin on a light bullet will cause a wobble jut like too slow a spin for a heavy bullet. I'm not sure if this will really come into play with the bullets and velocities of the .223/5.56 but I have an uncle that built a 7mm STW. He then loaded some bullets with 110gr TNT hollow-points. The end result was extremely poor accuracy - more than you would expect from just expect from a particular rifle "not liking" the bullet. We're talking inches off at 100 yards.

    That is an extreme example - again, I'm not sure that 1:7 - 1:9 twist rate is gonna make a big difference for a 16" barrel and a difference in bullet weight of 10-15gr.
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