chronograph

[RICHARD59]

Hello all: I bought a chronograph and need help. Will someone explain this for me how to figure the fpe I am getting out of the fps and weight of ammo. I know their must be a mathematical formula. thank you!

[Smoketown]

Chair Gun will do it for you.  Free at - http://www.hawkeoptics.com/chairgun.html
Just enter the values.

Or,

http://www.gatewaytoairguns.org/GTA/index.php?topic=10880.msg91915#msg91915

Cheers,
Smoketown

[Bill G]

For the sake of having the math on hand, I'll give you the problem

KE=1/2mass*velocity squared

KE= kinetic energy
mass= pellet weight
velocity = reading from the chrony

There is some conversion that has to occur.  pellet/ boolet weight in grains has to be converted to lbs and the method I dwill describe will do this for you.

pellet weight * velocity^2/( 7000 * 32.3 * 2)

25.4 * 900^2 / (7000 * 32.2 * 2)
20574000 / 450800
45.64

7000= 1lb in grains
32.3= gravity
2= the 1/2 in (KE=1/2 M*V^2)

Hope that helps.

Bill

[Ribbonstone]

Going to break it down even simpler.

velocity (in feet per second) X itself

divide that result by 450240

multiply that result by the pellet weight in grains.


So lets say 827fps with an 18grain pellet:

827 x 827 = 683929

683929 divided by 450240 =1.519032

1.519032 x 18 = 27.342576 (foot pounds)

[Gerard]

I do the calculation as above manually sometimes, but this online calculator makes it very easy:
http://www.airgunsofarizona.com/energycalc.htm

[RICHARD59]

Thanks Guys