Berger Bullets Twist Rate Stability Calculator suprises

Discussion in 'Rifles, Bullets, Barrels & Ballistics' started by TheDugg, May 27, 2015.

  1. TheDugg

    TheDugg Active Member

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    I dont know if im reading it all wrong. What does "Marginally stabile" mean in reality? According to the calculator the 150 grain barnes ttsx is not fully stabilized in a 1:11 or 1:12 twist barrel in .308w. That means I can forget about all Sako and Tikka rifles out there wich are 1:12 and 1:11 in .308w???
     
  2. elkaholic

    elkaholic Well-Known Member

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    In real life it means it would PROBABLY shoot well at closer ranges but may not as distance increases. This is why I don't like monos for long range work. BC suffers as well as twist required to stabilize them.......Rich
     
  3. TheDugg

    TheDugg Active Member

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    Thats true. I only use mono up to 300 yards in .308. But I also thinks its odd that Barnes use a 1:12 barrel in their load data for 150 ttsx. I've also seen shooters shooting remington LTR 1:12 barrel with 180 grains (lead) bullets with great accuracy on 300 yards. Is this "marginally stabilzed" more of an issue at really great distances like 600-1000 yards? Or else I cant understand why sako and tikka is stucked with 1:11 twist, all their models.
     
  4. elkaholic

    elkaholic Well-Known Member

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    I have not run the numbers so I couldn't say why Barnes uses a 12 twist. The elevation that the bullet is being used has considerable affect though. As I said, if you are only shooting 300 yards, and they are listed as "marginally" stable, you will probably be just fine.
     
  5. MMERSS

    MMERSS Well-Known Member

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    Marginal gyroscopic stability doesn’t necessarily mean the bullet will tumble but rather has a tendency to fly with more pitching and yawing than a bullet that is “more”stable. Marginal stable bullets could fly with a motion causing reduced drag and in essence reduces the effective BC of the bullet.
     
  6. BryanLitz

    BryanLitz <b>Official LRH Sponsor</b>

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    Solid bullets are longer for the same weight as a conventional lead core bullet. In general, longer bullets need faster twist to stabilize.

    Having said that, if you're in the 'Marginal' stability zone, that doesn't mean your groups or accuracy will suffer, but the bullet will fly with less BC than it would have if fully stabilized.

    As has been stated above, if your limit is 300 yards, the slight reduction in BC won't hurt you very much; you probably won't notice it.

    Take care,
    -Bryan
     
  7. TheDugg

    TheDugg Active Member

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    Thank you for your answere!
     
  8. Gerard Schultz

    Gerard Schultz Well-Known Member

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    The opposite is true as well. When solid copper bullets and lead core bullets are the same length, they will have very similar gyroscopic stability. There would be no need for a tighter twist rate to stabilize the bullet. The solid copper bullet would be lighter though and that brings the advantages of speed, shorter time of flight, similar momentum and usually more energy.