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Applied Ballistics for LR shooting ??s
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<blockquote data-quote="BryanLitz" data-source="post: 298239" data-attributes="member: 7848"><p>J,</p><p></p><p>Congrats on finishing the book! And thanks for the testamonial words, I just might use that in a future upgrade to my book selling page.</p><p></p><p>It's actually not as long as it seems, those last 175+ pages are not really to be read like the rest of it.</p><p></p><p>To answer your question, no. Form factor and drag coefficient are not the same thing. </p><p></p><p>Every shape has a unique drag coefficient at a given Mach number (velocity). Form factor is how the drag coefficient of one bullet relates to the drag coefficient of a standard bullet.</p><p></p><p>Let's say that projectile A has a drag coefficient of .250 at Mach 3, and that the 'G7 standard projectile' has a drag coefficient of .242 at the same Mach number. In this case, you would say that 'projectile A' has a G7 form factor of .250/.242 = 1.033.</p><p></p><p>Now if you take that same 'projectile A' and define it's form factor in relation to a different standard projectile, then it's form factor is different. For example, the drag coefficient (cd) of the G1 standard projectile is .513 at Mach 3. So the G1 form factor of projectile A is .250/.513 = .487.</p><p></p><p>So drag coefficient is a property of a projectile, and form factor is how the drag coefficient compares to a standard projectile.</p><p></p><p>The above example is on page 524 in the appendix.</p><p></p><p>Going from form factor to BC is easy, you just divide the sectional density by form factor. For example, if projectile A is a .308 caliber 155 grain bullet, then it's sectional density is: 155/7000/.308^2 = .233. To define this bullets BC in relation to the G7 standard, you would use the G7 form factor of 1.033. So the G7 BC is: .233/1.033 = .226. If you want to define this projectile's BC in reference to the G1 standard, then it's .233/.487 = .478.</p><p></p><p>You make a good observation about porting data from PPC to PC. I'll keep that in mind when I start work on my mobile software.</p><p></p><p>As for helping you with your analysis, I'm happy to answer questions when I have time. However, if you want me to actually get involved in doing any work that takes time, well, that's why I started my ballistics consulting business.</p><p></p><p>Now, Grass-Hoppa, go forth and put holes in distant targets!</p></blockquote><p></p>
[QUOTE="BryanLitz, post: 298239, member: 7848"] J, Congrats on finishing the book! And thanks for the testamonial words, I just might use that in a future upgrade to my book selling page. It's actually not as long as it seems, those last 175+ pages are not really to be read like the rest of it. To answer your question, no. Form factor and drag coefficient are not the same thing. Every shape has a unique drag coefficient at a given Mach number (velocity). Form factor is how the drag coefficient of one bullet relates to the drag coefficient of a standard bullet. Let's say that projectile A has a drag coefficient of .250 at Mach 3, and that the 'G7 standard projectile' has a drag coefficient of .242 at the same Mach number. In this case, you would say that 'projectile A' has a G7 form factor of .250/.242 = 1.033. Now if you take that same 'projectile A' and define it's form factor in relation to a different standard projectile, then it's form factor is different. For example, the drag coefficient (cd) of the G1 standard projectile is .513 at Mach 3. So the G1 form factor of projectile A is .250/.513 = .487. So drag coefficient is a property of a projectile, and form factor is how the drag coefficient compares to a standard projectile. The above example is on page 524 in the appendix. Going from form factor to BC is easy, you just divide the sectional density by form factor. For example, if projectile A is a .308 caliber 155 grain bullet, then it's sectional density is: 155/7000/.308^2 = .233. To define this bullets BC in relation to the G7 standard, you would use the G7 form factor of 1.033. So the G7 BC is: .233/1.033 = .226. If you want to define this projectile's BC in reference to the G1 standard, then it's .233/.487 = .478. You make a good observation about porting data from PPC to PC. I'll keep that in mind when I start work on my mobile software. As for helping you with your analysis, I'm happy to answer questions when I have time. However, if you want me to actually get involved in doing any work that takes time, well, that's why I started my ballistics consulting business. Now, Grass-Hoppa, go forth and put holes in distant targets! [/QUOTE]
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