This is my design for a potato cannon. According to my calculations the chamber is exactly 1.5:1 ratio to the barrel so it should be very efficient. In some testing I was able to launch a golf ball over 300 yards. It will shoot everything from potatoes to paint balls and fits nicely in a car because the barrel unscrews from the chamber. It is powered by loading the projectile down the barrel with a ramrod then pointing it towards the ground. The end cap can then be unscrewed and the chamber is filled with propane for a few seconds. Since propane is heaver than air it will sink to the bottom of the chamber. The cap is screwed back on and with a twist of the flint igniter the cannon fires.

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