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1:8 or 1:9

Discussion in 'Rifle Country' started by bigred94, Dec 13, 2009.

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  1. bigred94

    bigred94 Member

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    hi there i need some help. i am building a ar15 varmint,table gun. i am now ready to order my barrel, when ordering one must choose a 1:8 twist or 1:9 twist, whats the difference? seems to me that little of a difference will not make much difference on paper. gun will be a 600-1000 yard gun. what should i choose?
     
  2. haldir

    haldir Member

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    1:8, is more versatile.
     
  3. SomeKid

    SomeKid Member

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    IIRC, long range shooting in .223 tend to go for heavier bullet weights, as such, you would probably be better served with a 1:8.
     
  4. HOLY DIVER

    HOLY DIVER Member

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    if i was shooting 600-1000yards i would look at a 1:7 twist......in fact i think i would look into a dpms 308 ar style rifle for that kinda range
     
  5. Taurus 617 CCW

    Taurus 617 CCW Member

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    I put a Noveske 1:7 14.5" barrel on my AR and never looked back. It has been the best purchase I have ever made for an AR.
     
  6. Fatelvis

    Fatelvis Member

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    I prefer minimum 1:8 twist.
     
  7. Uncle Mike

    Uncle Mike Member

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    1:8" if you must but a 1:7" would be better if your going to shoot the long, heavy bullets out there at 1K.
     
  8. wishin

    wishin Member

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    All other things being equal, while a 1:7 handles (stabilizes?) a heavier bullet more effectively, how does it punch at 1000 yds compared to the 1:8?
     
  9. W.E.G.

    W.E.G. Member

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    What the heck does "punch" mean?

    Are you talking about kinetic energy?
    Rest assured, no matter what bullet you shoot out of a .223 at 1000 yards, the only "punch" it has at 1000 yards is enough energy to make it through the target-backer.
     
  10. Jim Watson

    Jim Watson Member

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    80 gr SMK is going to arrive at 1000 yds with 225 ft lbs.
    About like a light bullet .38 Special.

    Rifling twist has no effect on "punch" just stability.
     
  11. mljdeckard

    mljdeckard Member

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    And remember, the original rifling was 1/12. The army was using 55 gr bullets that were much more rounded, more like a football. They were intentionally making them yaw, it was very common to get sideways imprints of the bullets going through the paper at longer ranges. When they switched to the A2, they also switched to a 62 gr bullet, which is longer and the edge that touches the rifling (the ogive) is flat. The reason for 1/7 rifling is that tracers need a bit more stabilization than regular rounds. (I have fired tracers in machine guns, but never in an M-16.)

    In my experience, 1/9 handles everything very well, including 55 gr bullets. Particularly Barnes all-copper bullets, because they are a bit longer and flatter than lead bullets. The twist rate has just as much to do with the SHAPE of the bullet as it does the WEIGHT.
     
  12. Maverick223

    Maverick223 Member

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    It will generally make a smaller hole in the paper, because it didn't keyhole the heavy bullet that you tried to use in the 1:8" twist. :neener:

    To the O.P.: I would suggest going with a different chambering if you really want to reach out to 1k, the 6.5Grendel is probably the best candidate in a AR-15 platform and the .260 is even better in a AR-10 (but will be heavier by a good margin). If you are determined to go with .223, it will get the job done, but I would want a 1:6.5" or at least a 1:7" twist to handle the heavier (read: longer) bullets with a high BC.

    :)
     
  13. sarduy

    sarduy Member

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    1:7 so you can use the 55gr for closer range and the heavier bullets for long range
     
  14. Shadow Man

    Shadow Man Member

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    Like Maverick said, for reliable 1K hits, the 6.5 Grendal would be a better performing cartridge, yet, I will answer your question: out of the choices, 1:8 would be better, but may I suggest looking around for a 1:7 twist, or one even lower? Also, be careful of the length of bullets you start loading to get that high BC, eventually the rounds will no longer fit in the magazine. Now, if you had a bolt gun, it would be a totally different story...
     
  15. hoppes-no9

    hoppes-no9 Member

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    mljdeckard,

    Perhaps I am misreading your post, but it seems you are saying that in a given barrel, longer bullets stabilize better than shorter bullets of equal weight?

    If that is indeed what you're saying, that's wrong. Shorter bullets will stabilize better (unless you get into the area of "overstabilization"). Stated another way, longer bullets need faster twist to stabilize.

    twist calculator

    If I misunderstood your post, my apologies.
     
    Last edited: Dec 13, 2009
  16. wishin

    wishin Member

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    You can't serious? While it may not be in your guns and ammo lexicon, punch must surely imply more to a brilliant man like you than that.
     
  17. Maverick223

    Maverick223 Member

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    I calculated it to be 288ft/lb of energy with a 90gr projectile moving at 2500fps (which should be about right for "best case"), whether that is good enough for anything beyond paper is up to you. Personally, it is a little low for my taste.

    :)
     
  18. mljdeckard

    mljdeckard Member

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    I'm sorry if I was unclear, I was saying that 1/9 is a great compromise that will handle everything from 55 gr to 62 gr. I honestly haven't tried anything heavier than that.
     
  19. wishin

    wishin Member

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    I don't disagree that it's low, but I wouldn't want to get hit by the 225-280 ft.lbs that it would deliver at that range. I also think that a .308 or 6.5 Grendel would be a better choice.
     
  20. Maverick223

    Maverick223 Member

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    Huh? In the above quote I was referring to the fact that a heavy bullet would keyhole rather than punch a clean hole. FWIW, I'd rather not get shot with anything, including a BB gun, doesn't mean I consider that to have adequate power either, though 288fpe would be fine for most varmints (assuming P-dogs, G-hogs, et cetera).
     
  21. jbech123

    jbech123 Member

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    I shoot 77gr black hills factory loads in my 9 twist all the time, and it doesn't keyhole. In fact it shoots extremely well, and difference in group size between the 77gr, 62 gr, and 69gr is almost certainly inconsistency on my part, not my rifle.
     
  22. T.A.Sharps

    T.A.Sharps Member

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    I was in the same worry as the OP, being more accuracy oriented with my purchase.

    Basically the twist rate is directly related to the bullet you want to, or can shoot.

    I ended up going with a 1/9" twist barrel for half the reason I wanted a heavier/stiffer barrel for my 16" carbine, and the other half is that 95% of all 223/556 ammo available in my area is 55gr.

    I would really prefer to shoot 60-80 grain bullets, but I don't reload yet, and that ammo is more expensive and has less commercial options locally.

    I would rather of had a black coated 18" bull barrel with a 1/8 twist, and all the ammo to shoot, but it didn't seem realistic, if I start reloading I can always get a new Krieger barrel and free float tube for it.
     
  23. bigred94

    bigred94 Member

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    thanks for all the help, just one thing what does keyhole mean? also i am looking at the 69, 75 and 77 grain, what i understand the 1:8 will work best right?
     
  24. jbech123

    jbech123 Member

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    keyhole means the bullet hits the target sideways, or really any way besides point first. This can happen if the bullet is not spun fast enough to stabilize it. The longer/heavier bullets need to be spun faster to stabilize. For your needs an 8 twist would work, but if you handload and are thinking you might go to 80 or above, it wouoldn't hurt to get a 7 twist. The only disadvantage is you could have issues if you shoot really light bullets(like 40 gr) with really thin jackets. I've heard you can basically spin the bullet apart, although I've not ever witnessed this happening.
     
  25. wishin

    wishin Member

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