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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Long bullets require fast twist barrels?
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<blockquote data-quote="Michael Courtney" data-source="post: 864702" data-attributes="member: 28191"><p>The Miller twist rules predict Sg. In 2009, Bryan Litz assigned an expected accuracy of about 10% based on his experience with lots of different bullets. Since then, more careful testing and development of an improved formula to handle the case of plastic tipped bullets shows that the expected accuracy is now as good as 5% for solid metal bullets and plastic tipped bullets. </p><p></p><p>Larger uncertainties still apply to hollow point and open tipped match bullets due to the empty air space in the front. The Miller twist formula underestimates the stability of these bullets, and if there is a big empty volume in the nose of the bullet, the error can be significant. We are in the process of developing a more accurate formula for open tipped match and hollow point bullets that will use the depth of the open tipped portion to correct the formula for improved accuracy.</p><p></p><p>Once formulas are proven to make accurate predictions within 5-10%, I think they need not be referred to as "rule of thumb" and can be applied with confidence within their expected uncertainties.</p></blockquote><p></p>
[QUOTE="Michael Courtney, post: 864702, member: 28191"] The Miller twist rules predict Sg. In 2009, Bryan Litz assigned an expected accuracy of about 10% based on his experience with lots of different bullets. Since then, more careful testing and development of an improved formula to handle the case of plastic tipped bullets shows that the expected accuracy is now as good as 5% for solid metal bullets and plastic tipped bullets. Larger uncertainties still apply to hollow point and open tipped match bullets due to the empty air space in the front. The Miller twist formula underestimates the stability of these bullets, and if there is a big empty volume in the nose of the bullet, the error can be significant. We are in the process of developing a more accurate formula for open tipped match and hollow point bullets that will use the depth of the open tipped portion to correct the formula for improved accuracy. Once formulas are proven to make accurate predictions within 5-10%, I think they need not be referred to as "rule of thumb" and can be applied with confidence within their expected uncertainties. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Long bullets require fast twist barrels?
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