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Rifles, Reloading, Optics, Equipment
Reloading
Do you consider Sectional Density when choosing a bullet?
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<blockquote data-quote="Hugnot" data-source="post: 2261028" data-attributes="member: 115658"><p>Are BC values inconsistent and vary with velocity and air density?</p><p></p><p>From Berger: BC = SD/FF.</p><p></p><p>My thinking:</p><p></p><p>The SD, weight & diameter and the FF or shape of the bullet, remain constant or independent or is fixed during the bullet's flight making BC a constant value - unless the bullet blows up.</p><p></p><p>Drag (force) is variable caused by differences in air density and drag introduced by unstable bullets like inadequate twist rate.</p><p></p><p>Some ballistic programs and APs play around with BC and/or initial velocities to make calculations fit the actual trajectory.</p><p></p><p>I like the Hornady 4DOF ballistic calculator because it does not use BC, SD, or FF values to calculate performance - Doppler radar data.</p><p></p><p>The Hornady 4DOF calculator indicates that some pointy, light weight, high velocity bullets perform real good at extended ranges and these bullets incidentally have good SD (high) & FF (low) values. 22 Creedmoor fans appreciate this.</p><p></p><p>SD is good to look at.</p></blockquote><p></p>
[QUOTE="Hugnot, post: 2261028, member: 115658"] Are BC values inconsistent and vary with velocity and air density? From Berger: BC = SD/FF. My thinking: The SD, weight & diameter and the FF or shape of the bullet, remain constant or independent or is fixed during the bullet's flight making BC a constant value - unless the bullet blows up. Drag (force) is variable caused by differences in air density and drag introduced by unstable bullets like inadequate twist rate. Some ballistic programs and APs play around with BC and/or initial velocities to make calculations fit the actual trajectory. I like the Hornady 4DOF ballistic calculator because it does not use BC, SD, or FF values to calculate performance - Doppler radar data. The Hornady 4DOF calculator indicates that some pointy, light weight, high velocity bullets perform real good at extended ranges and these bullets incidentally have good SD (high) & FF (low) values. 22 Creedmoor fans appreciate this. SD is good to look at. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Reloading
Do you consider Sectional Density when choosing a bullet?
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