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Rifles, Reloading, Optics, Equipment
Rifles, Bullets, Barrels & Ballistics
True muzzle velocity
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<blockquote data-quote="ss7mm" data-source="post: 423546" data-attributes="member: 5"><p>The info below is from a Google search.</p><p>=============================================</p><p></p><p>There is a formula that will closely estimate this loss at normal chronograph distances:</p><p> </p><p>You will need a scientific calculator to do the calculation. If you don't have one. Window's calculator will work. Click Start ~ All Programs ~ Accessories ~ Calculator to bring it up. Then click the "View" menu and select "Scientific".</p><p> </p><p>On a scientific calculator, the "e" function is the inversion of "ln" (log number) function and that is activated by pushing "shift" or "inv" + the "ln" key.</p><p> </p><p>Now:</p><p> </p><p>Let CD = The Distance, in feet, from the muzzle to the center of the chronograph screens.</p><p>Let BC = The Ballistic Coefficient of the bullet.</p><p>Let CV = The average of the shot chronograph values.</p><p>Let MV = The Muzzle Velocity calculated from the Chronograph Velocity.</p><p> </p><p>Then</p><p> </p><p>e( CD / BC / 8816) x CV = MV</p><p> </p><p>Here's how to do it.</p><p> </p><p>CD = 7 feet.</p><p>BC = 0.300</p><p>CV = 1500 fps</p><p> </p><p>On your calculator, enter the following, being sure to enter the parentheses "( )" characters in the equation. The (*) may also be entered as (X) on a hand held calculator and the "=" may be entered as "EXE" or "Calc"</p><p> </p><p><em><span style="color: blue">"shift" + "ln" ( 7 / 0.3 / 8816 ) * 1500 =</span></em></p><p> </p><p><span style="color: black">This should return an answer of 1503.975 fps</span></p><p> </p><p><span style="color: #000000">Let's do my 280 Remington shooting a Hornady 139 gr. bullet with average chronograph values of 2818 fps</span></p><p> </p><p><span style="color: #000000">Chronograph distance is 15 feet.</span></p><p><span style="color: #000000">Ballistic Coefficient of the Hornady Bullet is 0.392</span></p><p> </p><p><em><span style="color: blue">e( 15 / 0.392 / 8816 ) x 2818 = </span></em></p><p> </p><p><span style="color: black">This returns a Muzzle Velocity of 2830 fps</span></p></blockquote><p></p>
[QUOTE="ss7mm, post: 423546, member: 5"] The info below is from a Google search. ============================================= There is a formula that will closely estimate this loss at normal chronograph distances: You will need a scientific calculator to do the calculation. If you don't have one. Window's calculator will work. Click Start ~ All Programs ~ Accessories ~ Calculator to bring it up. Then click the "View" menu and select "Scientific". On a scientific calculator, the "e" function is the inversion of "ln" (log number) function and that is activated by pushing "shift" or "inv" + the "ln" key. Now: Let CD = The Distance, in feet, from the muzzle to the center of the chronograph screens. Let BC = The Ballistic Coefficient of the bullet. Let CV = The average of the shot chronograph values. Let MV = The Muzzle Velocity calculated from the Chronograph Velocity. Then e( CD / BC / 8816) x CV = MV Here's how to do it. CD = 7 feet. BC = 0.300 CV = 1500 fps On your calculator, enter the following, being sure to enter the parentheses "( )" characters in the equation. The (*) may also be entered as (X) on a hand held calculator and the "=" may be entered as "EXE" or "Calc" [I][COLOR=blue]"shift" + "ln" ( 7 / 0.3 / 8816 ) * 1500 =[/COLOR][/I] [COLOR=black]This should return an answer of 1503.975 fps[/COLOR] [COLOR=#000000]Let's do my 280 Remington shooting a Hornady 139 gr. bullet with average chronograph values of 2818 fps[/COLOR] [COLOR=#000000]Chronograph distance is 15 feet.[/COLOR] [COLOR=#000000]Ballistic Coefficient of the Hornady Bullet is 0.392[/COLOR] [I][COLOR=blue]e( 15 / 0.392 / 8816 ) x 2818 = [/COLOR][/I] [COLOR=black]This returns a Muzzle Velocity of 2830 fps[/COLOR] [/QUOTE]
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