(A29) Are "potato guns" or "spud guns" legal?
"Potato guns" or "spud guns" generally consist of sections of PVC plastic tubing and fittings and are designed to launch a muzzle-loaded potato (or other similar-size projectile) using hair spray or other aerosol vapor as a propellant. The propellant is ignited by means of a barbecue grill igniter or other similar ignition system.
ATF has previously examined "potato guns" or "spud guns" as described above and has generally determined that such devices using potatoes as projectiles and used solely for recreational purposes are not weapons and do not meet the definition of "firearm" or "destructive device" in either the NFA or GCA. However, ATF has classified such devices as "firearms" and "destructive devices" if their design, construction, ammunition, actual use, or intended use indicate that they are weapons. For example, ATF has classified such devices as "firearms" and "destructive devices" if they are designed and used to expel flaming tennis balls.
Dammit! Now I have to dismantle in my flaming tennis ball gun!