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Computing Foot Pounds Of Energy At Various Distances

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13 August 2010, 21:46
BigFiveJack
Computing Foot Pounds Of Energy At Various Distances
Well guys, RIP provided me with the math formula to determine Sectional Density; and
GaryVA provided me with the math formula to determine when a cartridge is "Overbore".
So now I ask is there a math formula to determine FOOT POUNDS OF ENERGY at various
distances if the bullet diameter, bullet weight, and muzzle velocity is known? Soooooo,
anybody??? Why not a hot 7mm as the example? (.284" diam bullet, 175 grain weight,
3200 FPS at the muzzle) Thank you guys, very much.



Jack

OH GOD! {Seriously, we need the help.}

13 August 2010, 22:15
Antelope Sniper
Yes, the formula is:

velocity x velocity x mass / 450240
Velocity is in FPS
Mass is in grains

Inorder to get the formula to work on a standard 8 diget calculator it works best to do it this way:

{(velocity x velocity)/450240} x mass.
13 August 2010, 22:25
BigFiveJack
Thanks A.S. And I just found this:

Energy (ftlbs) = (Velocity x Velocity) x Weight (grains)] รท 450,240

BUT, at a remote distance, we now need a way to know the velocity out there!

So how do we determine if the muzzle velocity is 3200, what will it be at 1000 meters?



Jack

OH GOD! {Seriously, we need the help.}

13 August 2010, 22:42
Antelope Sniper
Plug your info in here:

http://www.jbmballistics.com/cgi-bin/jbmtraj-5.1.cgi

dancing
13 August 2010, 23:07
Grandpasez
Most loading programs and manuals give you
downrange velocity for various bullets knowing
the muzzle velocity.

For energy you can simplify formula by multiplying
the fps in hundreds; times grains and divide
by 45. Get rid whole bunch of zeros and do it simple

Example 1000gr at 3000 fps. Simple way--
3000 fps is 30, 0ne hundreds---

30 x 30 =900 x 1000gr = 900,000 divided by 45 = 20,000 ft lbs.Ed


MZEE WA SIKU
14 August 2010, 07:44
BigFiveJack
Thanks Ed. Big Grin Thanks again A.S.



Jack

OH GOD! {Seriously, we need the help.}