How this calculator works
The energy method inverts translational kinetic energy. The pressure method converts ideal pressure-volume work into projectile kinetic energy, starting from rest and ignoring barrel friction, gas leakage, moving gas energy and pressure variation beyond the entered average. It cannot infer peak chamber pressure or a loading specification. Distance divided by time is average speed over a short post-muzzle interval, approximating muzzle speed only if deceleration over that interval is negligible.
Formula
v=sqrt(2E/m); E=P_average A L; A=pi d^2/4; v_ideal=sqrt(2P_average A L/m); v_average=distance/time.
Worked example
A 0.02 kg projectile with 100 J of kinetic energy travels at 100 m/s. Covering 30 m in 0.1 s gives a measured average speed of 300 m/s.
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Frequently asked questions
Does average pressure mean peak chamber pressure?
No. The ideal work calculation requires average net pressure over the acceleration length.
Can the ideal model predict a real loading configuration?
No. It leaves out the changing gas state, friction and other internal-ballistics effects.
Why is flight distance divided by time only an estimate?
It measures average speed between two points. Drag makes that smaller than the launch speed when deceleration is appreciable.