BTW: I use a spark plug on my hybrid. All I can say is when I have the perfect mix and the fan running for 10 seconds it's makes one of thoses f****** sharp BANG
It's like in a combustion gun...the pressure is created by heat from a combustion....if you use sugar + KNO3 to generate pressure, the pressure will rise for a few seconds and then come back to atmospheric pressure.
Regulation pool balls are 2 1/4" in diameter so the barrel might need sleaving. If a regular pool ball have a diameter of 2 1/4" , 2.5" sch80 pvc pipe might be the best. Following McMaster chart the ID of 2.5" sch80 is 2.290". So there will be a 0.04 gap and mcmaster sell it only 18,36$ for 5' :D P...