Oh Thanks JSR, this is soooo cooool, the second picture look so efficient, it have the minie bullet effect and very long "barrel".

JSR, please feel free if you want to make this one. I dont have any access to make this, even this is so simple and efficient making the projectile and trigger gonna ...

Technically, with a bit of tweaking and some moderately high pressure, this should outperform a burst disk and be easier to reset.
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http://i823.photobucket.com/albums/zz151/lunkprab/untitled3.jpg


This is my design with longer "barrel", and better aerodynamic projectile. But ...

Can this simple cannon work?
The trigger just stop the projectile being fired, and the O ring hold the air from leaking.
My idea came from spetsnaz ballistic knife, As I know ballistic knife is so powerful with spring, if it replaced with 150 PSI compressed air I think its gonna be so cool ...