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Long Range Hunting & Shooting
Sectional density, ballistic coefficient and wind drift
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<blockquote data-quote="Aragorn50" data-source="post: 155483" data-attributes="member: 8024"><p>Ballistic coefficient and velocity are both important. Ballistic coefficient is a mathematical factor that allows us to use formulas to calculate bullet path. It can best be thought of as a measure of how much "drag" a projectile has as it travels though the atmosphere. Factors that affect ballistic coefficient include:</p><p>1. Sectional density: (how much mass or weight a projectile has compared to it's diameter) Thus all other things being equal, a longer projectile of the same material will have more weight and a higher sectional density.</p><p>2. Shape or form factor: This includes both the front and rear of the projectile. Projectiles with a longer ogive will have less drag. Secant ogives are somewhat more efficient than tangent ogives. The length and angle of the boattail and whether or not it is rebated also play a role.</p><p></p><p>The essential concept has to do with time of flight(TOF). The shorter the TOF, the less time gravity and wind will have to alter the bullet path. Thus initial velocity and rate of velocity loss are both important. Bullets with higher BC's will lose less velocity than bullets with a lower BC. This makes the TOF shorter and thus gravity has less time to cause the bullet to drop, and wind has less time to push it off of it's initial path. Higher BC = less drag = shorter TOF all other factors being equal.</p></blockquote><p></p>
[QUOTE="Aragorn50, post: 155483, member: 8024"] Ballistic coefficient and velocity are both important. Ballistic coefficient is a mathematical factor that allows us to use formulas to calculate bullet path. It can best be thought of as a measure of how much "drag" a projectile has as it travels though the atmosphere. Factors that affect ballistic coefficient include: 1. Sectional density: (how much mass or weight a projectile has compared to it's diameter) Thus all other things being equal, a longer projectile of the same material will have more weight and a higher sectional density. 2. Shape or form factor: This includes both the front and rear of the projectile. Projectiles with a longer ogive will have less drag. Secant ogives are somewhat more efficient than tangent ogives. The length and angle of the boattail and whether or not it is rebated also play a role. The essential concept has to do with time of flight(TOF). The shorter the TOF, the less time gravity and wind will have to alter the bullet path. Thus initial velocity and rate of velocity loss are both important. Bullets with higher BC's will lose less velocity than bullets with a lower BC. This makes the TOF shorter and thus gravity has less time to cause the bullet to drop, and wind has less time to push it off of it's initial path. Higher BC = less drag = shorter TOF all other factors being equal. [/QUOTE]
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Sectional density, ballistic coefficient and wind drift
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