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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Help with BC calculation
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<blockquote data-quote="chessman" data-source="post: 35214" data-attributes="member: 2451"><p>Ok, this is fun. I'm an aerospace engineer. I love ballistics. I can't explain everything, but I enjoy the study. First, a published BC should have been determined by testing over a variety of distances. What happens when we plug what we think we know into an equation, and the results don't match our prediction? We have long discussions about it on forums. Most of these posts focus on trying to prove that the measurement must be off rather than discussing whether or not the equation was correct. Some constant, variable, or group of variables must be incorrect if the results don't match the prediction. </p><p></p><p>What makes one drag function more correct than another? If a certain standard drag equation defines a particular bullet shape, what happens if you build a different shape bullet? The answer is that the equation that defines the performance of one bullet doesn't fit all other bullets. BC is part of the equation. - just one variable. Change a constant, like the shape of the bullet, and the relationship of all the variables changes also.</p><p></p><p>When a BC is published, do the manufacturers give you all the math behind their claims? What drag function best describes their bullet at a given velocity? Never have seen that on a box of bullets.</p><p></p><p>The best way to predict bullet drop is to do exactly what Jerry is doing - measure the results and then try to find an equation that defines them. No single formula can fit all the variables. In this case, the G7 drag function more closely matches the measured results than the G1. </p><p></p><p>F=MA</p></blockquote><p></p>
[QUOTE="chessman, post: 35214, member: 2451"] Ok, this is fun. I'm an aerospace engineer. I love ballistics. I can't explain everything, but I enjoy the study. First, a published BC should have been determined by testing over a variety of distances. What happens when we plug what we think we know into an equation, and the results don't match our prediction? We have long discussions about it on forums. Most of these posts focus on trying to prove that the measurement must be off rather than discussing whether or not the equation was correct. Some constant, variable, or group of variables must be incorrect if the results don't match the prediction. What makes one drag function more correct than another? If a certain standard drag equation defines a particular bullet shape, what happens if you build a different shape bullet? The answer is that the equation that defines the performance of one bullet doesn't fit all other bullets. BC is part of the equation. - just one variable. Change a constant, like the shape of the bullet, and the relationship of all the variables changes also. When a BC is published, do the manufacturers give you all the math behind their claims? What drag function best describes their bullet at a given velocity? Never have seen that on a box of bullets. The best way to predict bullet drop is to do exactly what Jerry is doing - measure the results and then try to find an equation that defines them. No single formula can fit all the variables. In this case, the G7 drag function more closely matches the measured results than the G1. F=MA [/QUOTE]
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Help with BC calculation
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