muzzle velocity??

[shadowghost21]

I have GGDT and im trying to use it to find a muzzle velocity of a nerf gun. Since nerf guns have no valves I dont know how to use GGDT without a valve, it is just a spring compression piston. You guys know how nerf works but nay way I need a work around for GGDT or a way to work out a pressure equaltion. P1V1=P2V2 where P1 is the current pressure of the atmosphere where you live and V1 is the volume of the chamber when the piston is compressed. I solved to P2 and put that into GGDT but had to tweak a lot of numbers to get a velocity that made any sense. But if you guys know how I could find the velocity of a projectile or recompute the pressure. A work around for GGDT??

[boilingleadbath]

My geuss is that the slow pressure rise from the movement of the piston will interfere with your predections.

Maybe you could model this by having a large dead space, and a momentarily-open "generic" valve?
(but hell if I know...)

[shadowghost21]

sounds good I will try that it should work, what value should I put into the 'Open Time' about 1000ms or more, and for the dead space I use half of my total volume.