Author: **SpudBlaster15** » Sun Oct 14, 2007 10:47 pm

A rough estimation of velocity can be obtained using the formula v^2 = 2*a*s, where v = final velocity (m/s), a = acceleration(m/s<sup>2</sup>), and s = displacement (meters).

In order to solve this equation, you will need to find acceleration using the equation a = f/m, where a = acceleration (m/s<sup>2</sup>), f = force (newtons), and m = mass (kilograms). To find the force exerted on the projectile in order to solve this equation, multiply the average barrel pressure (pascals) by the surface area of the projectile's face (m<sup>2</sup>).

Pressure drop is P1 * V1/(V1 + V2), where P1 = initial chamber pressure, V1 = chamber volume, and V2 = volume of air behind the projectile at a given position in the barrel. You will need this to calculate the average pressure in the barrel, and thus average force on the projectile.

This method isn't *really* accurate (c'mon, it's average acceleration), as it doesn't account for gas flows, or static and dynamic projectile friction, but it provides a fairly reasonable estimate for heavy projectiles and fast opening, high flow valves.

Last edited by

SpudBlaster15 on Sun Oct 14, 2007 11:54 pm, edited 3 times in total.

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