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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
The science to twist rates
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<blockquote data-quote="Mikecr" data-source="post: 451716" data-attributes="member: 1521"><p>This is a common fallacy with stability. It's not true, and so fails many tests.</p><p></p><p>You might recognize that a twist requirement is in displacement per turn(12:1).</p><p>The displacement is typically assumed standard sea level density air.</p><p>There is no time, or velocity rates in this requirement.</p><p></p><p>Why is that? </p><p>Afterall, if technically 'just below' Sg of 1.0(barely stable, possibly), and you bump velocity way way up, you could technically raise Sg to >1.0, and not tumble. Well, because another 10deg drop in temp can again result in tumbling no matter adjusted velocity.</p><p>That's one of many tests that could fail here, and the truth always passes all tests.</p><p>Also, 'Just below' or 'Just barely' stable performs so badly that it is NEVER considered viable in twist requirements (ideal is Sg 1.5).</p><p></p><p>So you will never see bullet makers assigning RPM requirements, because it would be woefully incorrect to do so, and cause hardship to many customers.</p><p>Sorry for the rant, but this RPM perspective really must be quashed.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 451716, member: 1521"] This is a common fallacy with stability. It's not true, and so fails many tests. You might recognize that a twist requirement is in displacement per turn(12:1). The displacement is typically assumed standard sea level density air. There is no time, or velocity rates in this requirement. Why is that? Afterall, if technically 'just below' Sg of 1.0(barely stable, possibly), and you bump velocity way way up, you could technically raise Sg to >1.0, and not tumble. Well, because another 10deg drop in temp can again result in tumbling no matter adjusted velocity. That's one of many tests that could fail here, and the truth always passes all tests. Also, 'Just below' or 'Just barely' stable performs so badly that it is NEVER considered viable in twist requirements (ideal is Sg 1.5). So you will never see bullet makers assigning RPM requirements, because it would be woefully incorrect to do so, and cause hardship to many customers. Sorry for the rant, but this RPM perspective really must be quashed. [/QUOTE]
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The science to twist rates
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