Barrel length question with GGDT

[air_dannon]

Hi,

I have a pen gun with a barrel sealing piston (okay, not really a "pen"... more like a fat marker). I tried punching in the numbers for GGDT, but there are inputs I'm not quite sure about...

I made a diagram with the sizes and diameters I know in the jpeg below. I'm wondering what GGDT will say about my barrel length.

I'd appreciate it if someone could crunch the numbers and show a screenshot of GGDT? I promise to make a fun damage video when the marker gun is done :blackeye:

[jackssmirkingrevenge]

Here you go, not the most impressive performance in the world but pneumatics, even HPA ones, tend to prefer long barrels for that to be the case.

If for example I keep all parameters equal but increase barrel length to 10 inches, I get 9 ft-lbs of energy, double of the current configuration.

[air_dannon]

Hey! Thanks JSR. Glad you saw my distress call. I made the barrel length 8" and narrowed the bore to 0.25". This is the new specs I believe. It's shooting nails through wood real nice now

[jackssmirkingrevenge]

Sorry for the late reply, but glad you made it in the end did you post the finished project?

[air_dannon]

Not yet. I'll do that soon, hopefully with a video too.