Twist Rate

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  • Twist Rate

    Hi all,

    Am just wondering what the difference is between a 1-8 twist rate as opposed to a 1-12 twist rate. I understand in the respect to how many twists in the barrel but what I'm really wanting to hear from you all is what's the benefit of each in their own respect.. Heavy projectiles etc?? My .223 is a 1-12 but am looking at something else or maybe setting mine up for long range shoots.

    Many Thanks

    Dan

  • #2
    Put simply a faster twist such as a 1:8 will stabilise longer/heavier projectiles than a 1:12. While over stabilization doesn't affect accuracy as bad as under stabilized bullets it is better to select the right twist for the length/weight of the intended projectile of use.

    Comment


    • Jason Lefty
      Jason Lefty commented
      Editing a comment
      Originally posted by Atirau" post=18597
      Put simply a faster twist such as a 1:8 will stabilise longer/heavier projectiles than a 1:12. While over stabilization doesn't affect accuracy as bad as under stabilized bullets it is better to select the right twist for the length/weight of the intended projectile of use.
      This is true but by playing around with the amount of powder you use the 1:12 twist will work with the longer/heavier projectiles to. Guess my point is you can make both twist rates work if you play around with powder lvls. To much powder on a twist rate like 1:8 will over stabiles the projectile where it might be good for the 1:12. Also the barrel length comes into play with this to. Shorter barrels like the tighter twist rates so there is a lot you got to take into account.

  • #3
    I only have a basic understanding so i wont try to explain it in detail but it goes a little like this. Something about the center of gravity (COG) trying to overtake the center of force (COF) [bullet wants to tumble] and needing enough gyroscopic force (twist) to over come this. Heavier bullet = longer (for same cal) therefore greater distance between COG & COF and more leverage pushing COG ahead of COF therefore more gyroscopic force is needed to stop it tumbling.

    I did find this video helpful, though it explains it in excruciating detail:

    http://www.youtube.com/watch?v=Z3h0pMQAFUU
    List to tick off:
    - TICK!!! NEW SCOPE: Sightron S-tac 2.5-17.5 X 56mm
    - TICK !!Left handed 223rem, Zastava M85
    - wildcat build in progress: 223McShort
    - TICK!!! Rebarrel Howa to 7mm-08
    - TICK!!! case trimmer/turner
    - Comp dies for 7mm-08
    - Case annealer
    - Custom dies for wild cat

    Comment


    • #4
      Rule of thumb:
      1:12 = up tp 55gn
      1:8 = 55gn - 80gn
      Obviously depends on bullet type as faster twist rate is needed for longer bullets (these are generally heavier).

      55gn is a good all rounder small to med game. So either twist rates are fine for general this.

      1:12 with lighter proj good as a vermin rilfle (flatter shooting / varmint type rifle). Closer range target work
      1:8 with heavier proj allows for bigger game (goats pigs etc.) and obviously requires more hold over for longer dist shots. More stable for longer range.

      Comment


      • El-Skippo
        Skip commented
        Editing a comment
        Originally posted by Vromme" post=18621
        Rule of thumb:
        1:12 = up tp 55gn
        1:8 = 55gn - 80gn
        Obviously depends on bullet type as faster twist rate is needed for longer bullets (these are generally heavier).

        55gn is a good all rounder small to med game. So either twist rates are fine for general this.

        1:12 with lighter proj good as a vermin rilfle (flatter shooting / varmint type rifle). Closer range target work
        1:8 with heavier proj allows for bigger game (goats pigs etc.) and obviously requires more hold over for longer dist shots. More stable for longer range.
        1-12 is about 62 grn max bit have heard people getting 65 grn to shoot good also.

        1-12 50-55 grn are the best suited for that twist. But you can shoot lighter pills if need too.

        1-8 will shoot the heavy stuff (80 grn max ) down to about 50 grn ( my own experience was not to shoot lighter then 50 grn pills of the HP kind, they tend to explode in the air a few meters from the muzzle.)

    • #5
      Or, if like me on this computer you don't have Excel you can use the JBM Ballistics Bullet Stability Calculator.

      http://www.jbmballistics.com/cgi-bin/jbmstab-5.1.cgi

      Comment


      • #6
        This got me curious. I'm buggered if I know what my 223's twist rate is so had to look it up. On Tikka's website

        What is the twist rate in 223 Rem. caliber Tikka heavy barrel?
        All the twist rates are given in the Tikka specification sheets and datatables. The rate of twist of a Tikka T3 in cal. 223 Rem is 8”.
        Ah, I have a 1:8 twist. Guess I'm good to go with all ammo. I usually use 55gn stuff so all good

        Comment


        • Guest's Avatar
          Guest commented
          Editing a comment
          Originally posted by Mister" post=20071
          This got me curious. I'm buggered if I know what my 223's twist rate is so had to look it up. On Tikka's website

          What is the twist rate in 223 Rem. caliber Tikka heavy barrel?
          All the twist rates are given in the Tikka specification sheets and datatables. The rate of twist of a Tikka T3 in cal. 223 Rem is 8”.
          Ah, I have a 1:8 twist. Guess I'm good to go with all ammo. I usually use 55gn stuff so all good
          A .223R Tikka T3 can be either a 1:12" or 1:8" and the twist rate should be stamped on the left side of the barrel for a right handed rifle. That goes for all models irrespective of what their FAQ says, have a look at the data table for Tikka T3.
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