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Barrel length question with GGDT

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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Barrel length question with GGDT

Unread postAuthor: air_dannon » Sat Aug 29, 2015 3:07 pm

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:
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Re: Barrel length question with GGDT

Unread postAuthor: jackssmirkingrevenge » Mon Sep 07, 2015 8:15 pm

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.

air_dannon_ggdt.jpg


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.
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Re: Barrel length question with GGDT

Unread postAuthor: air_dannon » Wed Sep 09, 2015 8:08 pm

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 :wink:
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Re: Barrel length question with GGDT

Unread postAuthor: jackssmirkingrevenge » Fri Sep 11, 2015 6:34 am

Sorry for the late reply, but glad you made it in the end ;) did you post the finished project?
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Re: Barrel length question with GGDT

Unread postAuthor: air_dannon » Fri Sep 11, 2015 8:51 am

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