Don't Mess with Texas
This was my first cannon ever built, and it used a ghetto shrader propane meter. Only God knows where that is now. The chamber is 12" of 4" pvc, and 36-40" of 2" barrel. Piezo ignition, and the shoddy barrel knife helped with shooting spuds. Fun to learn on, but not quite a showpiece.
The Carrot Shooter
This has an ungodly cb ratio to start with. 12" of 2" chamber and probably just shy of 2' of 1/2" barrel. Piezo ignition, aerosol propelled. As the name says, carrots were primary ammo. Notice custom faded paintjob.

Nothing special, these are just from the past, so please spare me the noob flaming.