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<blockquote data-quote="Jon A" data-source="post: 52006" data-attributes="member: 319"><p>Actually, BC is a direct function of the weight of the bullet. Length has little to do with it (except that heavy bullets tend to be longer, aerodynamic shapes--long ogives, sharp points and boattails--tend to make the bullets longer). The length of the bullet itself, with other factors held constant has only a small contribution to drag.</p><p></p><p>The BC of a bullet is directly proportional to its sectional density which, in turn, is directly proportional to its weight.</p><p></p><p>What this means is that if you have two bullets with identical shapes but one is twice as heavy as the other, the heavy one will have a BC exactly twice as high as the light one.</p><p></p><p>The BC isn't just a measure of how much aerodynamic drag a bullet has. It's a measure of that <em>as well as</em> how well the bullet will resist this drag.</p><p></p><p>So think about the bullets above, with identical shape but one is twice as heavy as the other. They will have the same amount of drag. The air will slow them down by applying the same force of drag. It will change their velocity by decelerating them (or causing negative acceleration). This acceleration is equal to the force divided by the mass (per f=ma).</p><p></p><p>So with the same force of drag applied, the heavy bullet will be decelerated at only 1/2 the rate of the light bullet. It will hold onto its velocity twice as well as the light bullet...thus, the twice as big a BC.</p><p></p><p>Clear as mud?</p><p></p><p>That's why I've been toying with the thought of getting into swaging one of these days...and messing with Tungsten core bullets. Tungsten is 1.7 times as dense as lead, it's pretty cheap and widely available. Can anybody say, "30 caliber, 300 grain bullet with a BC of over 1.0?" <img src="http://images/icons/grin.gif" alt="" class="fr-fic fr-dii fr-draggable " style="" /></p><p></p><p>Anyway, here's what this means in practice:</p><p></p><p>When comparing bullets with similar shapes, the lighter ones will have lower BC's.</p><p></p><p>Performance-wise, the lighter bullets at higher velocities will shoot flatter until the heavier bullet "catches up." But often the heavier bullet won't "catch up" trajector-wise until a range far beyond your maximum.</p><p></p><p>So why use the heavy bullet?</p><p></p><p>First reason is wind drift. Given similar shapes, a heavy bullet will always drift less in the wind than the lighter bullet even with its lower velocity. BC is everything when it comes to wind drift. You won't "make it up" with extra velocity, even at relatively close ranges. With a rangefinder and a drop chart, drop can be accounted for. The wind on the other hand is much more difficult. Having a bullet that only drifts 1/2 as much will make whatever skills you have at reading the wind that much better.</p><p></p><p>The second is retained energy. The people here aren't just punching a hole in a piece of paper. If your "super-duper-ultra-wizbang" magnum only hits as hard as a 22LR way out there, it won't kill very well. The heavy bullet with the high BC will retain more energy and hit harder way out there.</p><p></p><p>An exception to the rule is when you compare bullets with different shapes. A light bullet with a much more aerodynamic shape, such as Warrens, or GS's (possibly, I don't know how accurate his advertised BC's are) launched at a high velocity can outperform a less aerodynamic heavy bullet in all areas out to your maximum range. In that case, you have the benefit of a much flatter trajectory which could help if you find yourself hunting "medium ranges" without a rangefinder.</p><p></p><p>**DISCLAIMER**</p><p></p><p>Warren, anybody, feel free to correct anything wrong I've said above. I'm not an accomplished long range shooter like many on this site...just a ballistics nerd!</p></blockquote><p></p>
[QUOTE="Jon A, post: 52006, member: 319"] Actually, BC is a direct function of the weight of the bullet. Length has little to do with it (except that heavy bullets tend to be longer, aerodynamic shapes--long ogives, sharp points and boattails--tend to make the bullets longer). The length of the bullet itself, with other factors held constant has only a small contribution to drag. The BC of a bullet is directly proportional to its sectional density which, in turn, is directly proportional to its weight. What this means is that if you have two bullets with identical shapes but one is twice as heavy as the other, the heavy one will have a BC exactly twice as high as the light one. The BC isn't just a measure of how much aerodynamic drag a bullet has. It's a measure of that [I]as well as[/I] how well the bullet will resist this drag. So think about the bullets above, with identical shape but one is twice as heavy as the other. They will have the same amount of drag. The air will slow them down by applying the same force of drag. It will change their velocity by decelerating them (or causing negative acceleration). This acceleration is equal to the force divided by the mass (per f=ma). So with the same force of drag applied, the heavy bullet will be decelerated at only 1/2 the rate of the light bullet. It will hold onto its velocity twice as well as the light bullet...thus, the twice as big a BC. Clear as mud? That's why I've been toying with the thought of getting into swaging one of these days...and messing with Tungsten core bullets. Tungsten is 1.7 times as dense as lead, it's pretty cheap and widely available. Can anybody say, "30 caliber, 300 grain bullet with a BC of over 1.0?" [img]images/icons/grin.gif[/img] Anyway, here's what this means in practice: When comparing bullets with similar shapes, the lighter ones will have lower BC's. Performance-wise, the lighter bullets at higher velocities will shoot flatter until the heavier bullet "catches up." But often the heavier bullet won't "catch up" trajector-wise until a range far beyond your maximum. So why use the heavy bullet? First reason is wind drift. Given similar shapes, a heavy bullet will always drift less in the wind than the lighter bullet even with its lower velocity. BC is everything when it comes to wind drift. You won't "make it up" with extra velocity, even at relatively close ranges. With a rangefinder and a drop chart, drop can be accounted for. The wind on the other hand is much more difficult. Having a bullet that only drifts 1/2 as much will make whatever skills you have at reading the wind that much better. The second is retained energy. The people here aren't just punching a hole in a piece of paper. If your "super-duper-ultra-wizbang" magnum only hits as hard as a 22LR way out there, it won't kill very well. The heavy bullet with the high BC will retain more energy and hit harder way out there. An exception to the rule is when you compare bullets with different shapes. A light bullet with a much more aerodynamic shape, such as Warrens, or GS's (possibly, I don't know how accurate his advertised BC's are) launched at a high velocity can outperform a less aerodynamic heavy bullet in all areas out to your maximum range. In that case, you have the benefit of a much flatter trajectory which could help if you find yourself hunting "medium ranges" without a rangefinder. **DISCLAIMER** Warren, anybody, feel free to correct anything wrong I've said above. I'm not an accomplished long range shooter like many on this site...just a ballistics nerd! [/QUOTE]
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