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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Ballistic Program Inconsistencies
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<blockquote data-quote="BryanLitz" data-source="post: 312259" data-attributes="member: 7848"><p>Jeff,</p><p></p><p>Thank you for sharing your expertise!</p><p></p><p>I've also found small differences in the Siacci solutions compared to numerical integration. I suspected that it had to do with a definition of Cd vs Mach, but never tracked it down. I just applied a correction factor (about 1 or 2 percent) to the air density that resulted in very good matches at long range.</p><p></p><p>Another compromise in the Siacci approach (at least the implementation given in McCoy) is that the integrals use velocity as the independent variable. The problem is that temperature changes the speed of sound, which changes the CD vs velocity relationship (not the CD vs Mach relationship); so when you get away from standard temperature, the tables are off. It's a small amount, and doesn't tend to matter much, but is one of those things that will, as you said, cause solutions to diverge as you get away from standard atmosphere.</p><p></p><p>The software you've written, is it available commercially?</p><p></p><p>What's are your thoughts on the Pejsa solution?</p><p></p><p>It's good to know there are other 'geeks' out there who are pay attention to this stuff!</p><p></p><p>-Bryan</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 312259, member: 7848"] Jeff, Thank you for sharing your expertise! I've also found small differences in the Siacci solutions compared to numerical integration. I suspected that it had to do with a definition of Cd vs Mach, but never tracked it down. I just applied a correction factor (about 1 or 2 percent) to the air density that resulted in very good matches at long range. Another compromise in the Siacci approach (at least the implementation given in McCoy) is that the integrals use velocity as the independent variable. The problem is that temperature changes the speed of sound, which changes the CD vs velocity relationship (not the CD vs Mach relationship); so when you get away from standard temperature, the tables are off. It's a small amount, and doesn't tend to matter much, but is one of those things that will, as you said, cause solutions to diverge as you get away from standard atmosphere. The software you've written, is it available commercially? What's are your thoughts on the Pejsa solution? It's good to know there are other 'geeks' out there who are pay attention to this stuff! -Bryan [/QUOTE]
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Rifles, Reloading, Optics, Equipment
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Ballistic Program Inconsistencies
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