How to Make a Potato Gun

First you need these materials:
4" PVC pipe
2" PVC pipe
4" female
4" plug
4" coupler
4" reducer

You take the 4" pipe and and cap it off with a 4" female pipe item, and then put the plug on that end to close the combustion chamber. On the other end of the 4" pipe you place the coupler and the reducer to make the pipe go from 4" to 2". Then place the 2" pipe or barrel through the reducer. After this you must glue everything into place with cement glue. All that is left now is to add the spark generator and you can put this anywhere on the side of the combustion chamber. Now you can place the potato in the barrel and shoot your gun!!
http://www.youtube.com/watch?v=ykF3TUTI2hU