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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
.220 Swift - Non Lead - 1:14 twist
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<blockquote data-quote="scope-eye" data-source="post: 2158535" data-attributes="member: 21274"><p>[URL unfurl="true"]http://bulletin.accurateshooter.com/2008/06/calculating-bullet-rpm-spin-rates-and-stability/[/URL]</p><p>Go to bottom othe page to the last paragraph.</p><p>Or even better from they article</p><p></p><p>"That said, we note that bullet-makers provide a recommended twist rate for their bullets. This is the "safe bet" to achieve stabilization with that bullet, and it may also indicate the twist rate at which the bullet shoots best. Though the RPM number alone does not assure gyroscopic stability, an RPM-based calculation can be very useful. We've seen real world examples where a bullet that needs an 8-twist barrel at 2800 FPS MV, would stabilize in a 9-twist barrel at 3200 FPS MV. Consider these examples"</p><p></p><p>Dean</p><p></p><p><strong>MV = 2800 FPS</strong></p><p><strong>8-Twist RPM = 2800 x (12/8) x 60 = 252,000 RPM</strong></p><p><strong></strong></p><p><strong>MV = 3200 FPS</strong></p><p><strong>9-Twist RPM = 3200 x (12/9) x 60 = 256,000 RPM</strong></p></blockquote><p></p>
[QUOTE="scope-eye, post: 2158535, member: 21274"] [URL unfurl="true"]http://bulletin.accurateshooter.com/2008/06/calculating-bullet-rpm-spin-rates-and-stability/[/URL] Go to bottom othe page to the last paragraph. Or even better from they article "That said, we note that bullet-makers provide a recommended twist rate for their bullets. This is the “safe bet” to achieve stabilization with that bullet, and it may also indicate the twist rate at which the bullet shoots best. Though the RPM number alone does not assure gyroscopic stability, an RPM-based calculation can be very useful. We’ve seen real world examples where a bullet that needs an 8-twist barrel at 2800 FPS MV, would stabilize in a 9-twist barrel at 3200 FPS MV. Consider these examples" Dean [B]MV = 2800 FPS 8-Twist RPM = 2800 x (12/8) x 60 = 252,000 RPM MV = 3200 FPS 9-Twist RPM = 3200 x (12/9) x 60 = 256,000 RPM[/B] [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
.220 Swift - Non Lead - 1:14 twist
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