One more thing I just read about:
Will I be able to fill the chamber fast enough to close the valve? If i have a 2ft long 2" pipe?

Thanks for the help man, After messing with GGDT i think I will go with the 2". ANd posibly make the Mini paintball launcher if I have some extra time/chash

Seeing as you put it that way I might stay with the 2" PVC I have. I do not have a plumbing store anywere near by to my knowing. Are bushings the flat reducers? I think I used one on my potato cannon. If so then I have a place to buy it.

Thanks for all the help. I was hoping for help like this ...

Thanks for the Help Daberno,
No I was not looking for step by step. Just some help.
And would it just be easier to have the chamber bigger than 2" Dia? And would I be able to fill the chamber if it is lets say 3" dia? I will have to do the volume math..
Sully

The better configuration would be to install the sprinkler directly behind the barrel breech. The 180 becomes just part of the air tank at that point and your dead space is minimized.
Do you mean that when I make a cannon, I should have it go from the chamber, to a 90* then another 90* then to ...

I am looking to build my first air cannon and was hoping for help. I am Looking for something of smaller size but i can not pick a cannon. One of my choices is the Mini Paintball Launcher at Free Paintball Plans, It is the small size that is nice, but it is almost too small. And I would have to buy ...