GGDT Design Library


Originally designed as a "Bazooka" for paintball scenario games (a use it never actually saw), my "Shorty" air gun is probably about the closest thing one can find to a "typical" air gun. It uses the ubiquitous 1" Orbit WaterMaster (modified for pneumatic operation, of course). It's layout is simple and straight forward. It is neither high-powered nor overly small. In other words, it's a good specimen for study because any data produced is likely to be of interest to a large number of air gunners out there (Details of the gun design should be self evident based on the photograph and examination of the GGDT data file linked at the bottom of this page.).

My procedure for modeling Shorty was quite simple. I fired a number of shots at known pressures and measured the velocities. For each pressure I found an average velocity. I then plugged those averages into the Cv/Kv/Eff Tool and let GGDT determine a valve flow coefficient for the valve. Once that was complete I plugged the (average) flow coefficent back into the model to see how well GGDT was sticking to the curve. Note that I would have liked to have fired a more shots but all the neighborhood dogs were going nuts (Shorty's kinda loud!) and I didn't wanna push my luck.

Pressure Measured
75 psi 269 263 2.2%
70 psi 262 256 2.3%
60 psi 239 239 0.0%
50 psi 220 220 0.0%
30 psi 158 167 5.7%

In the coming days it will be interesting to get back out and do some more testing. Even more interesting will be to see how a gun of similar configuration with the same valve compares. But for now? I'm pretty happy with the results.

If you'd like the model I used, right click on it and save it as a file...


PS: For those who are interested, my raw shot data is as follows...

Pressure Measured fps
75 269
70 261, 269, 260, 258
60 239
50 221, 217, 221
30 162, 163, 155, 155

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