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Rifles, Reloading, Optics, Equipment
Reloading
224 Valkyrie Bullet Choices for 6.5 Twist Barrel
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<blockquote data-quote="RegionRat" data-source="post: 2810741" data-attributes="member: 57231"><p>A 6.5 twist is pretty far up the scale of being a really fast twist for a 22 caliber bullet.</p><p></p><p>At some point, the rotation of the bullet (RPM) creates a centrifugal force that can distort the bullet. At some RPM rates, bullets can even disintegrate.</p><p></p><p>The 1:6.5 isn't common in 224. It exists mostly to serve F-T/R and folks who are wanting to push 85.5 and 90 gr bullets, but even there you have to watch out for issues with very high RPM rates if the velocity is also high.</p><p></p><p>The simple version is RPM = Muzzle Velocity x 720/twist</p><p></p><p>For example a 224V pushing a 90 grain at 2650 fps with a 7 twist will be (2650x(720/7))= 272,571 RPM and has an SG of 1.35 so it gives up about 4% on the BC.</p><p>The same 224V at a 6.5 Twist will be 293,539 RPM with an SG of 1.56</p><p></p><p>The question to ask is if the bullet will distort or blow up at 294k RPM? If you had to, you could back off and it would still be stable.</p><p></p><p>Some manufacturers will answer those questions over the phone and know the rough limits of their bullets. I would give them a ring.</p><p></p><p>Good Luck and in for the range report.</p></blockquote><p></p>
[QUOTE="RegionRat, post: 2810741, member: 57231"] A 6.5 twist is pretty far up the scale of being a really fast twist for a 22 caliber bullet. At some point, the rotation of the bullet (RPM) creates a centrifugal force that can distort the bullet. At some RPM rates, bullets can even disintegrate. The 1:6.5 isn't common in 224. It exists mostly to serve F-T/R and folks who are wanting to push 85.5 and 90 gr bullets, but even there you have to watch out for issues with very high RPM rates if the velocity is also high. The simple version is RPM = Muzzle Velocity x 720/twist For example a 224V pushing a 90 grain at 2650 fps with a 7 twist will be (2650x(720/7))= 272,571 RPM and has an SG of 1.35 so it gives up about 4% on the BC. The same 224V at a 6.5 Twist will be 293,539 RPM with an SG of 1.56 The question to ask is if the bullet will distort or blow up at 294k RPM? If you had to, you could back off and it would still be stable. Some manufacturers will answer those questions over the phone and know the rough limits of their bullets. I would give them a ring. Good Luck and in for the range report. [/QUOTE]
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224 Valkyrie Bullet Choices for 6.5 Twist Barrel
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