Instead of using a ball valve or other such contrivance to dump air directly from a reservoir into the chamber of this PVC air cannon, [Ben] is using a much more clever design. This is a barrel ...

Standard: Based on the Plast-O-Matic “Engineered ” True Blue Ball Valve with dual floating seats and Trunnion design. 15 º, 30 °, 45 º, 60 °, 90 ° V-Balls ...