Spud gun A spud gun is a small toy gun used to fire a fragment of potato. To operate, one punctures the surface of a potato with the gun's hollow tip and pries out a small pellet which fits in the muzzle. Squeezing the grip causes a small build-up of air pressure inside the toy which propels the projectile. The devices are usually short-range and low-powered. The first spud gun was invented during the Great Depression. The original inventor sold his patent to E. Joseph Cossman for US$600 after World War II. Cossman, the brother-in-law of "Uncle" Milton Levine, sold two million spud guns in six months as a result of an advertising campaign.