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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
calculating bc
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<blockquote data-quote="FEENIX" data-source="post: 453762" data-attributes="member: 14204"><p>The formula for calculating the ballistic coefficient for bullets <em>only</em> is as follows:<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-0" target="_blank">[1]</a><a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-1" target="_blank">[2]</a></p><p> <img src="http://upload.wikimedia.org/math/c/4/9/c494b0416825cdc5fa71474121f6dfa0.png" alt="" class="fr-fic fr-dii fr-draggable " style="" /> where:</p><p> </p><ul> <li data-xf-list-type="ul"><em>BCBullets</em> = ballistic coefficient</li> <li data-xf-list-type="ul"><em>SD</em> = <a href="http://en.wikipedia.org/wiki/Sectional_density" target="_blank">sectional density</a>, SD = mass of bullet in <a href="http://en.wikipedia.org/wiki/Pound_%28mass%29" target="_blank">pounds</a> or <a href="http://en.wikipedia.org/wiki/Kilogram" target="_blank">kilograms</a> divided by its caliber squared in inches or meters; units are lb/in2 or kg/m2.</li> <li data-xf-list-type="ul"><em>i</em> = form factor, <em>i</em> = <img src="http://upload.wikimedia.org/math/c/5/7/c5775a0e70c4d5800a4d3c3626abc121.png" alt="" class="fr-fic fr-dii fr-draggable " style="" />; (CG ~ 0.5191)</li> <li data-xf-list-type="ul"><em>CB</em> = Drag coefficient of the bullet</li> <li data-xf-list-type="ul"><em>CG</em> = Drag coefficient of the G1 model bullet</li> <li data-xf-list-type="ul"><em>M</em> = Mass of object, lb or kg</li> <li data-xf-list-type="ul"><em>d</em> = diameter of the object, in or m</li> </ul><p>This BC formula gives the ratio of ballistic efficiency compared to the standard G1 model projectile. The standard projectile originates from the "C" standard reference projectile defined by the German steel, ammunition and armaments manufacturer <a href="http://en.wikipedia.org/wiki/Krupp" target="_blank">Krupp</a> in 1881.<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-2" target="_blank">[3]</a> The G1 model standard projectile has a BC of 1.<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-3" target="_blank">[4]</a> The French Gavre Commission decided to use this projectile as their first reference projectile, giving the G1 name.<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-4" target="_blank">[5]</a><a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-5" target="_blank">[6]</a></p><p> A bullet with a high BC will travel farther than one with a low BC since it will retain its velocity better as it flies downrange from the muzzle, will resist the wind better, and will "shoot flatter" (see <a href="http://en.wikipedia.org/wiki/External_ballistics" target="_blank">external ballistics</a>).<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-6" target="_blank">[7]</a></p><p> When hunting with a rifle, a higher BC is desirable for several reasons. A higher BC results in a flatter <a href="http://en.wikipedia.org/wiki/Trajectory" target="_blank">trajectory</a> which in turn reduces the effect of errors in estimating the distance to the target. This is particularly important when attempting a clean hit on the vitals of a game animal. If the target animal is closer than estimated, then the bullet will hit higher than expected. Conversely, if the animal is further than estimated the bullet will hit lower than expected. Such a difference in bullet drop can often make the difference between a clean kill and a wounded animal.</p><p> This difference in trajectories becomes more critical at longer ranges. For some cartridges, the difference in two bullet designs fired from the same rifle can result in a difference between the two of over 30 cm (1 foot) at 500 meters (550 yards). The difference in impact energy can also be great because <a href="http://en.wikipedia.org/wiki/Kinetic_energy" target="_blank">kinetic energy</a> depends on the square of the velocity. A bullet with a high BC arrives at the target faster and with more energy than one with a low BC.</p><p> Since the higher BC bullet gets to the target faster, it is also less affected by the crosswinds.</p><p></p><p>(<a href="http://en.wikipedia.org/wiki/Ballistic_coefficient" target="_blank">http://en.wikipedia.org/wiki/Ballistic_coefficient</a>)</p><p></p><p>I like math but I'd leave this to the pros - ballisticians. <img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite8" alt=":D" title="Big Grin :D" loading="lazy" data-shortname=":D" /> Personally, I'd go with the published BC (and use programs like what's on this site) and play around with the actual performance, drops, mV, and other factors you want to measure out of your tweaked loads at varying distances. I'm sure the pros will chime in soon.</p><p></p><p>Good luck!</p><p></p><p>Ed</p></blockquote><p></p>
[QUOTE="FEENIX, post: 453762, member: 14204"] The formula for calculating the ballistic coefficient for bullets [I]only[/I] is as follows:[URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-0"][1][/URL][URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-1"][2][/URL] [IMG]http://upload.wikimedia.org/math/c/4/9/c494b0416825cdc5fa71474121f6dfa0.png[/IMG] where: [LIST] [*][I]BCBullets[/I] = ballistic coefficient [*][I]SD[/I] = [URL="http://en.wikipedia.org/wiki/Sectional_density"]sectional density[/URL], SD = mass of bullet in [URL="http://en.wikipedia.org/wiki/Pound_%28mass%29"]pounds[/URL] or [URL="http://en.wikipedia.org/wiki/Kilogram"]kilograms[/URL] divided by its caliber squared in inches or meters; units are lb/in2 or kg/m2. [*][I]i[/I] = form factor, [I]i[/I] = [IMG]http://upload.wikimedia.org/math/c/5/7/c5775a0e70c4d5800a4d3c3626abc121.png[/IMG]; (CG ~ 0.5191) [*][I]CB[/I] = Drag coefficient of the bullet [*][I]CG[/I] = Drag coefficient of the G1 model bullet [*][I]M[/I] = Mass of object, lb or kg [*][I]d[/I] = diameter of the object, in or m [/LIST] This BC formula gives the ratio of ballistic efficiency compared to the standard G1 model projectile. The standard projectile originates from the "C" standard reference projectile defined by the German steel, ammunition and armaments manufacturer [URL="http://en.wikipedia.org/wiki/Krupp"]Krupp[/URL] in 1881.[URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-2"][3][/URL] The G1 model standard projectile has a BC of 1.[URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-3"][4][/URL] The French Gavre Commission decided to use this projectile as their first reference projectile, giving the G1 name.[URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-4"][5][/URL][URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-5"][6][/URL] A bullet with a high BC will travel farther than one with a low BC since it will retain its velocity better as it flies downrange from the muzzle, will resist the wind better, and will “shoot flatter” (see [URL="http://en.wikipedia.org/wiki/External_ballistics"]external ballistics[/URL]).[URL="http://en.wikipedia.org/wiki/Ballistic_coefficient#cite_note-6"][7][/URL] When hunting with a rifle, a higher BC is desirable for several reasons. A higher BC results in a flatter [URL="http://en.wikipedia.org/wiki/Trajectory"]trajectory[/URL] which in turn reduces the effect of errors in estimating the distance to the target. This is particularly important when attempting a clean hit on the vitals of a game animal. If the target animal is closer than estimated, then the bullet will hit higher than expected. Conversely, if the animal is further than estimated the bullet will hit lower than expected. Such a difference in bullet drop can often make the difference between a clean kill and a wounded animal. This difference in trajectories becomes more critical at longer ranges. For some cartridges, the difference in two bullet designs fired from the same rifle can result in a difference between the two of over 30 cm (1 foot) at 500 meters (550 yards). The difference in impact energy can also be great because [URL="http://en.wikipedia.org/wiki/Kinetic_energy"]kinetic energy[/URL] depends on the square of the velocity. A bullet with a high BC arrives at the target faster and with more energy than one with a low BC. Since the higher BC bullet gets to the target faster, it is also less affected by the crosswinds. ([URL]http://en.wikipedia.org/wiki/Ballistic_coefficient[/URL]) I like math but I'd leave this to the pros - ballisticians. :D Personally, I'd go with the published BC (and use programs like what's on this site) and play around with the actual performance, drops, mV, and other factors you want to measure out of your tweaked loads at varying distances. I'm sure the pros will chime in soon. Good luck! Ed [/QUOTE]
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