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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
How important is bc?
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<blockquote data-quote="Fitch" data-source="post: 357221" data-attributes="member: 19372"><p>Wind drift is directly proportional to lag time. Lag time for a given bullet is defined as the difference between the flight time in a vacuum and the flight time in air to reach the distance of interest. </p><p> </p><p>Very simply:</p><p> </p><p>Wd = Ws * Tlag</p><p> </p><p>Wd = wind drift in feet</p><p>Ws = cross wind component speed in ft/sec</p><p>Tlag = lag time in seconds as defined above.</p><p> </p><p>This isn't complicated. Most ballistics programs will give time of flight in air. The time of flight in a vacuum is the distance in feet divided by the MV in ft/sec. For example, 300 feet /3,000 ft/sec = 0.1 second flight time to 100 yards in a vacuum for a bullet with 3,000 ft/sec muzzle velocity. </p><p> </p><p>BC gets into the act because it represents the physical properties (weight, cross sectional area, and form factor) that cause the lag time. The way BC is defined a higher BC bullet will have shorter lag time and thus less wind drift. BC is a convenient one number index of how well the bullet will penetrate the air with out losing velocity. </p><p> </p><p>Works for me anyway. </p><p> </p><p>Fitch</p></blockquote><p></p>
[QUOTE="Fitch, post: 357221, member: 19372"] Wind drift is directly proportional to lag time. Lag time for a given bullet is defined as the difference between the flight time in a vacuum and the flight time in air to reach the distance of interest. Very simply: Wd = Ws * Tlag Wd = wind drift in feet Ws = cross wind component speed in ft/sec Tlag = lag time in seconds as defined above. This isn't complicated. Most ballistics programs will give time of flight in air. The time of flight in a vacuum is the distance in feet divided by the MV in ft/sec. For example, 300 feet /3,000 ft/sec = 0.1 second flight time to 100 yards in a vacuum for a bullet with 3,000 ft/sec muzzle velocity. BC gets into the act because it represents the physical properties (weight, cross sectional area, and form factor) that cause the lag time. The way BC is defined a higher BC bullet will have shorter lag time and thus less wind drift. BC is a convenient one number index of how well the bullet will penetrate the air with out losing velocity. Works for me anyway. Fitch [/QUOTE]
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How important is bc?
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