Thanks! I think I'll stick with the coaxial design; at 2" the other example may prove to be more of a headache than I want to deal with. However, I do have one question for you... How is Big Red actuated? I still can't figure that one out...

I'm looking to put together a T-shirt cannon for a school project this January, and have been reading around on QDV design. "Officially" the project is for T-shirts, but I have access to nitrogen and helium and anticipate firing other projectiles. However, my question is in regard to the "vents" cut...