Thank you, Mr Crowley. I've researched piston valves before and they've just looked really obnoxious to build, I just never really noticed how simply they actually work.
I just had trouble concieving how gun freak's design worked (seeing as it's not a COMPLETE design, I didn't quit understand how it was pressurized when a valve for the main chamber wasn't labeled, I figured I was missing something about piston valves).
I've done a bolt-action sprinkler valve cannon before, so it's not that I'm lazy. But hey, thanks for helping me out anyways

But anywho, gun freak, are you wanting a sprinkler valve for this cannon?
And, you don't really want them for small scale (handheld) cannons because they are pretty expensive (around 30).