i have one that i made that is pretty much bad ass. It was powered by a 100,00 volt stun gun for ignition and has 3 points where it sparks in the tube for even ignition of the propellent. I used to use hair spray but then switched to propane. I have a setup that i calculated the exact air to fuel ratio and came up with the exact amount of propane needed. I also have interchangeable barrels and different grips for it. The last time we shot it the potato would go about 5-6 football fields i shit you not. It would hurt to fire. I have pics if anyone wants some lol