--OK, gang I want to build one; first order of business build a "scale model". I'm on a mission to acquire parts to build a 4" bore grapefruit gun. It's got to be "portable", i.e. transportable to events in a trailer. At present I've got a lead on a trailer, barrel material and a 4" quick-acting valve. Next I need a pressure vessel of around 200-300 gallon capacity, that can withstand about 200psi (double the planned 100psi operating pressure for safety). Holler if anyone sees same on the Left Coast. With luck I'll have something working in time to storm the "Vault of Heaven", heh.