What is a spudgun?
Spud guns, potato cannons, produce accelerators, or weapons of mashed destruction are all recreational launching devices usually made of plumbing pipe. There are two common means to launch projectiles from a spudgun. The first uses the energy stored in a compressed gas and the second, more popular method, uses the energy released by combusting fuel vapors to heat the air and cause it to expand. There is a quite rare mix of the two, a "hybrid", that combusts a pressurized fuel-air mixture. The object of these varieties is to propel projectiles in the direction of a designated (safe) target for fun. Common projectiles include: mandarins, potatoes, tennis balls, golf balls,bb's (if you have a small enough barrel), in fact pretty much any spare vegetable you can ram down the tube. This makes them a particularly popular home-made class of projectile launchers because of their low cost to build: a simple hairspray powered gun costs no more than $20 in PVC and glue, less if parts can be scrounged.
Please see the article on safety.