Thanks to all for your help. After the first couple shots, I had already redesigned the gun, so I made a gift of it to a friend; I've been trying to generate some local intetest in pumpkin chucking and it seemed like a good way to start. The new gun will be essentially the same, only with a 2" barre...

Regarding the 1:5:1 chamber/barrel ratio- If I understand correctly (and can do math) a 10"x4" chamber with a 30"x2" barrel would be 1:5:1, correct? Also, any suggestion as to what I might fire from a 3" barrel? I was considering small grapefruit or oranges. Potatoes obviously, if I can find some wi...

A pic

Duly noted, although I'm new enough at this to still consider the noise part of the attraction. Will post some pics and firing data after the weekend.

Thanks guys!

I'm about to build my second cannon and was hoping some of you veterans would offer some advice and/or stop me from ending up with a bunch of shrapnel in my head. Design is fairly simple (I think)- Expansion chamber is 4" x 15" Sch40 PVC Barrel is 3" x 30" Sch40 PVC 12v fan 5 Point pulse grill ignit...