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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Improved Stability Formula for Plastic Tipped Bullets
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<blockquote data-quote="Mikecr" data-source="post: 738780" data-attributes="member: 1521"><p>Do you know HOW this is so?</p><p>I searched both these reference documents and see no accounting of tipped bullets, or improvement to Miller's rule of thumb.</p><p></p><p>When Cma(overturning moment) rises, stability goes down.</p><p>Cma = X(Cp-Cg)</p><p>Cp & Cg are taken from bullet base</p><p>As bullets approach Mach1 Cp moves forward, reducing stability. So moving Cp forward is destabilizing.</p><p>Cg allows yard darts to fly point forward with no other forces acting to stabilize them.</p><p>For stability at a given spin rate, you keep center of gravity relatively close or forward w/resp to center of pressure.</p><p></p><p>The only way I could see a plastic tip NOT reducing stability, is if the solid plastic weighs as much or more than the copper hollow point it's displacing(holding Cg), or, if the smaller plastic meplat is moving Cp backwards on the bullet(without moving Cg), or both.</p><p></p><p>What doesn't make sense is that plastic tipped bullet stability would go up, while it's BC doesn't seem to change. Normally affecting one, affects the other(either up or down).</p><p>This is why I ask if you know HOW it does just this.</p></blockquote><p></p>
[QUOTE="Mikecr, post: 738780, member: 1521"] Do you know HOW this is so? I searched both these reference documents and see no accounting of tipped bullets, or improvement to Miller's rule of thumb. When Cma(overturning moment) rises, stability goes down. Cma = X(Cp-Cg) Cp & Cg are taken from bullet base As bullets approach Mach1 Cp moves forward, reducing stability. So moving Cp forward is destabilizing. Cg allows yard darts to fly point forward with no other forces acting to stabilize them. For stability at a given spin rate, you keep center of gravity relatively close or forward w/resp to center of pressure. The only way I could see a plastic tip NOT reducing stability, is if the solid plastic weighs as much or more than the copper hollow point it's displacing(holding Cg), or, if the smaller plastic meplat is moving Cp backwards on the bullet(without moving Cg), or both. What doesn't make sense is that plastic tipped bullet stability would go up, while it's BC doesn't seem to change. Normally affecting one, affects the other(either up or down). This is why I ask if you know HOW it does just this. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Improved Stability Formula for Plastic Tipped Bullets
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