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Shooting & Reloading - Mausers, Big Bores and others >> Rifles
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9.3x57
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CZ; 6.5x55 Twist Rate??? *DELETED*
      #95649 - 01/02/08 06:25 AM

Post deleted by 9ThreeXFifty7

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Nakihunter
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Re: CZ; 6.5x55 Twist Rate??? [Re: 9.3x57]
      #95656 - 01/02/08 10:33 AM

I haven't checked this but two things come to mind. The 8.6 twist is the original M96 twist for 156gr bullets in the 6.5X55. It would most probably be a metric twist which is roughly 1 in 220mm.

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9.3x57
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Re: CZ; 6.5x55 Twist Rate??? [Re: Nakihunter]
      #95660 - 01/02/08 11:42 AM

Naki:

Original twist for the 6.5x55 was 1/200mm {1 in 7.87"}, not 1/220.

But I think you might be on to something by mentioning the twist rate in metric. I've seen CZ material showing the twist to be 1/220, so maybe that's what it has always been and the material I saw was merely rounding it up.Various methods can be used to guess the required twist, but I've been curious as to how the CZ rifles do with long 140 grain bullets {some of which are quite a bit longer than the 156 and 160 grain bullets}. Since length governs twist rate, I've wondered if anyone has found any yaw present with long bullets on targets at say over 200 meters?

My calculation using Twist = [{.06 x Velocity} x {Diameter Squared}] / Bullet Length shows a need for a Twist of 7 inches for the Hornady 160 grain bullet. Such a twist does not of course exist on most rifles {Ruger is 1/8", CZ is 1/8.6" and many custom guns are 1/9"}. Nevertheless the bullets seem totally stable in my Ruger rifles.

IIRC, my formula is for bullets fired in excess of around 2200 fps.

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What are the Rosary, the Cross or the Crucifix other than tools to help maintain the fortress of our faith in Jesus Christ, the Son of God?

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