Chamber- 4.5ft of 3" pvc
Barrel- 6ft of 2" with a potato cutter tip
valve- moddified 2" sprinkler valve acctuated with 3/4" ball valve
psi range- 60 to 116psi( ear plugs are a must!)
other features- handle and shoulder strap and soon laser sighting.
primary ammo- potatos and lemons, soon I will fill an old spray can with water and freeze it

Thanks to pvc arsenal 17 and rna duelers for their help.
here are some pics, soon I'll have a dmg video I still need to edit it.
edit: this pic of it whole is misleading, the barrel is not at a steep angle as it looks in the pic. I had to take it from my balcony to get it all in, the cannon is lying on its side so it looks more angulated than it really is.
cheers
heres some melon carnage, quality isnt as good as I had hoped but you get the idea

more vids for you

http://youtube.com/watch?v=HeySSYWxxCc
http://youtube.com/watch?v=4BYFoxD0XGw
http://youtube.com/watch?v=GE0VWDRjxzU