This was a video that i did in my multi media class. And with a couple of friends too.
In this video i describe how to make a potato gun
first get a 2ft long 2 inch wide abs pipe
an adapter that goes from 2 to 3 inch abs pipe
a 1ft long 3 inch wide abs pipe
and a coupler with a cap on the back
Then get a bbq ignition lighter and set up the wires like a spark plug..
It would cost you about 30 dollars to make one including glue, pipes, and the bbq ignition.
So good luck and have fun. I know i did