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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
BEWARE, Problems with Exbal and G7 BC's
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<blockquote data-quote="BryanLitz" data-source="post: 448099" data-attributes="member: 7848"><p>Good point Mike.</p><p></p><p>Regarding Loadbase which uses Pejsa equations...</p><p></p><p>As I recall, the math used in the Pejsa equations defines drag as a function of velocity, not Mach number. This practice fails to capture the effects of temperature on Mach number and drag, which is real. The error would have the effect of predicting too much drop in low temperature.</p><p></p><p>The extra high drop predicted by Gerald's latest exbal suggest that he locked down the definition of speed of sound to the standard value, and removed the temperature dependence. 447" is excessive.</p><p></p><p></p><p></p><p>You can, by multiplying the ICAO BC by 1.018. Again, I'm assuming that exbal is using ASM. Careful with assumptions.</p><p></p><p>Interesting that exbal uses 29.92", 59 deg and 78% hum. Seems like a mixture of ASM and ICAO? I never heard of SAA, but it's a possibility that may explain why 1.8% doesn't <em>exactly</em> make up the difference.</p><p></p><p>-Bryan</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 448099, member: 7848"] Good point Mike. Regarding Loadbase which uses Pejsa equations... As I recall, the math used in the Pejsa equations defines drag as a function of velocity, not Mach number. This practice fails to capture the effects of temperature on Mach number and drag, which is real. The error would have the effect of predicting too much drop in low temperature. The extra high drop predicted by Gerald's latest exbal suggest that he locked down the definition of speed of sound to the standard value, and removed the temperature dependence. 447" is excessive. You can, by multiplying the ICAO BC by 1.018. Again, I'm assuming that exbal is using ASM. Careful with assumptions. Interesting that exbal uses 29.92", 59 deg and 78% hum. Seems like a mixture of ASM and ICAO? I never heard of SAA, but it's a possibility that may explain why 1.8% doesn't [i]exactly[/i] make up the difference. -Bryan [/QUOTE]
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BEWARE, Problems with Exbal and G7 BC's
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