I built a copy of the Mad Caddy this weekend. I used 4" PVC for the chamber and a 27 1/2" barrel. We tested it to day at 100psi and 110psi this thing is sweet!!! I know it's not an original it's a copy but why re-invent the wheel, it does what I want, sling golf balls like crazy.
I didn't get the name of the original builder of the Mad Caddy but He deserves all the credit for this one I just reused his work. So far everybody that has asked I have told them it was someone elses idea I just copied it with some minor changes.
