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<blockquote data-quote="LouBoyd" data-source="post: 264647" data-attributes="member: 9253"><p>The ballistic coefficients published by all bullet manufactures are based on the G1 model unless otherwise stated. (and it's rarely stated otherwise). Most bullet manufacturers don't even state what velocity the stated G1 BC is correct for, but the coefficient are generally close in the 2500 to 3500 fps range and usable from about 1500 to 4000. They're terrible in the transonic range. Sierra is unique that they usually publish 3 or 4 BCs for ranges of velocities. You'll find flat base spitzers fit the G1 curves fiarly well. </p><p></p><p>Why does everyone use G1? Pure marketing. The G1 numbers are bigger because the test projectile was higher drag than any other model. Wouldn't you want to buy a bullet with a 0.65 G1 BC than a 0.31 G7 BC? Just remember that while BCs do predict wind deflection, drop, and energy loss. They do not predict still air accuracy. Most accuracy records are set with relatively low BC bullets. </p><p></p><p>Dont agaonize over BCs Using G7 or G5 won't give you a significant improvemnt in results and you'll have to develop the measurements yourself if you wnat to use them There are just about no published values other than G1. Other G functions may be useful when trying to precisely "curve fit" you measured drops at different ranges then use the progam to fit other points in between. That may be useful if you shoot one bullet a lot, but you'll find it still won't fit perfectly. </p><p></p><p>If you want to understand what BCs mean and where BCs came from read "Modern Exterior Ballistics" by Robert L. McCoy of BRL. (Aberdeen Proving Grounds). THe book also discusses the limitations of ballistic computations. BCs arent the only limiting factor. . Even if drag tables were perfect there is a whole layer of calculaton limitiatins which aren't even addressed by conventional ballistic programs which would still limit accuracy. Those are the result of bullet yaw and precession. The math is available to do the more advanced calculations but there is no way to predict the input conditions accuratly enough for typical shooting to make those methods useful. It's also why you'll never see a spin stabilized rifle which shoots perfeclty . It's amazing some do as well as they do.</p></blockquote><p></p>
[QUOTE="LouBoyd, post: 264647, member: 9253"] The ballistic coefficients published by all bullet manufactures are based on the G1 model unless otherwise stated. (and it's rarely stated otherwise). Most bullet manufacturers don't even state what velocity the stated G1 BC is correct for, but the coefficient are generally close in the 2500 to 3500 fps range and usable from about 1500 to 4000. They're terrible in the transonic range. Sierra is unique that they usually publish 3 or 4 BCs for ranges of velocities. You'll find flat base spitzers fit the G1 curves fiarly well. Why does everyone use G1? Pure marketing. The G1 numbers are bigger because the test projectile was higher drag than any other model. Wouldn't you want to buy a bullet with a 0.65 G1 BC than a 0.31 G7 BC? Just remember that while BCs do predict wind deflection, drop, and energy loss. They do not predict still air accuracy. Most accuracy records are set with relatively low BC bullets. Dont agaonize over BCs Using G7 or G5 won't give you a significant improvemnt in results and you'll have to develop the measurements yourself if you wnat to use them There are just about no published values other than G1. Other G functions may be useful when trying to precisely "curve fit" you measured drops at different ranges then use the progam to fit other points in between. That may be useful if you shoot one bullet a lot, but you'll find it still won't fit perfectly. If you want to understand what BCs mean and where BCs came from read "Modern Exterior Ballistics" by Robert L. McCoy of BRL. (Aberdeen Proving Grounds). THe book also discusses the limitations of ballistic computations. BCs arent the only limiting factor. . Even if drag tables were perfect there is a whole layer of calculaton limitiatins which aren't even addressed by conventional ballistic programs which would still limit accuracy. Those are the result of bullet yaw and precession. The math is available to do the more advanced calculations but there is no way to predict the input conditions accuratly enough for typical shooting to make those methods useful. It's also why you'll never see a spin stabilized rifle which shoots perfeclty . It's amazing some do as well as they do. [/QUOTE]
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