This is my biggest cannon. I built it to do two things. (1) I built it to be huge. And (2) i build it to hurl potatos as far as i posibly could. It has a 1.5 inch barrel that is about 16 feet long and angled at 45 degrees. the chamber is 2 inch pvc and is 6 feet long, 3 feet tall, and 11 feet wide (you will see what i mean in the picture). If you look at the picture and are wondering why there is duct tape all over the barrel, its because its the only thing i could think of to attach the 0.5 inch alluminum pipe to make it a little more ridged. it just uses a ball valve, but it is so powerfull you can only see the potato for about a second, then its out of sight. i have shot it so much that i can open the valve extremly fast. I did have my friend be a spotter and he said it went 3 feilds, which is a little under 3/4 of a mile. He was able to see it because he was about 1/3 mile out, but out of the line of fire. One thing i realized after i built it is that i cant shoot at anything because the barrel is at such a high angle. Tell me what you think. I will eventually put a piston valve on it, i just need the money first!