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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
? about ballistic programs
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<blockquote data-quote="LouBoyd" data-source="post: 278714" data-attributes="member: 9253"><p>It depends on why your trajectory doesn't match the calculations.</p><p></p><p>Is the manufactures published BC wrong? Some are most are close.</p><p></p><p>Is your chronograph wrong? Maybe if you chronograph is triggering on the muzzle blast shockwave instead of the bullet.</p><p></p><p>Did you enter the scope/sight centerline over the bore correctly in the ballistics program? That's very important if you calulated clicks/moa to match. To nit pick that should be the distance the line of sight passes over the centerline of the bore >AT THE MUZZLE<. </p><p></p><p>It's not likely the calculations are significantly in error. Just about all software for PCs uses the same ballistic tables and basic equations </p><p>published by Robert F McCoy of the US Army Aberdeen Balistics Research Labs. There a notable exceptions like Art Pejsa's program. </p><p></p><p>So what's left? The atmosphere of course. </p><p></p><p>I mostly shoot at 5600' elevation. If I don't set the air density correctly the calculated trajectories are significantly different from actual trajectories. Air density can be calculated from temperature, standard barometic pressure, elevation, and humidity or it can be measured directly with an air density gauge which actually weighs a volume of air.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 278714, member: 9253"] It depends on why your trajectory doesn't match the calculations. Is the manufactures published BC wrong? Some are most are close. Is your chronograph wrong? Maybe if you chronograph is triggering on the muzzle blast shockwave instead of the bullet. Did you enter the scope/sight centerline over the bore correctly in the ballistics program? That's very important if you calulated clicks/moa to match. To nit pick that should be the distance the line of sight passes over the centerline of the bore >AT THE MUZZLE<. It's not likely the calculations are significantly in error. Just about all software for PCs uses the same ballistic tables and basic equations published by Robert F McCoy of the US Army Aberdeen Balistics Research Labs. There a notable exceptions like Art Pejsa's program. So what's left? The atmosphere of course. I mostly shoot at 5600' elevation. If I don't set the air density correctly the calculated trajectories are significantly different from actual trajectories. Air density can be calculated from temperature, standard barometic pressure, elevation, and humidity or it can be measured directly with an air density gauge which actually weighs a volume of air. [/QUOTE]
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Rifles, Bullets, Barrels & Ballistics
? about ballistic programs
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