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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Let's argue about BC's
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<blockquote data-quote="ZEEK" data-source="post: 475006" data-attributes="member: 29898"><p>If I understand history correctly, the BC was developed as a way to address the fact that the drag force is different on every type of projectile. So to simplify things and not have to make measurements of drag deceleation for every type of projectile, the BC was proposed as a method to scale the drag deceleation from one projectile, let's call it the "standard" projectile, to another projectile, our bullet if interest. So we see the BC is all about drag.</p><p> </p><p>Lots of things effect drag, the spin dampening moment is one of them. One of the factors of the spin dampening moment is angular velocity (how fast the bullet is spinning). So two projectiles with the same velocity, but different spin rates--the faster spinning projectile experiences more drag. The second thing that could play into this is the yaw angle. When a bullet leaves the barrel, the axis-of-rotation of the bullet does not exactly correspond with the axis of the barrel (due to barrel vibration and end effect from the end of the barrel), these differences in yaw angle will also effect bullet drag as the drag coefficient is a function of the yaw angle. The final thing is that the higher spin rate may also allow the yaw angle to more quickly reach the yaw of response (or equilibrium yaw).</p><p> </p><p>So we see a lot of factors come into play and can effect a bullet's BC. In the end, if you want good accurate data for yor rifle--go to te field and make good measurements.</p></blockquote><p></p>
[QUOTE="ZEEK, post: 475006, member: 29898"] If I understand history correctly, the BC was developed as a way to address the fact that the drag force is different on every type of projectile. So to simplify things and not have to make measurements of drag deceleation for every type of projectile, the BC was proposed as a method to scale the drag deceleation from one projectile, let's call it the "standard" projectile, to another projectile, our bullet if interest. So we see the BC is all about drag. Lots of things effect drag, the spin dampening moment is one of them. One of the factors of the spin dampening moment is angular velocity (how fast the bullet is spinning). So two projectiles with the same velocity, but different spin rates--the faster spinning projectile experiences more drag. The second thing that could play into this is the yaw angle. When a bullet leaves the barrel, the axis-of-rotation of the bullet does not exactly correspond with the axis of the barrel (due to barrel vibration and end effect from the end of the barrel), these differences in yaw angle will also effect bullet drag as the drag coefficient is a function of the yaw angle. The final thing is that the higher spin rate may also allow the yaw angle to more quickly reach the yaw of response (or equilibrium yaw). So we see a lot of factors come into play and can effect a bullet's BC. In the end, if you want good accurate data for yor rifle--go to te field and make good measurements. [/QUOTE]
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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
Let's argue about BC's
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