Originally Posted by: ericthecableguy...build a potato gun.

Potato guns should always be constructed, loaded, and operated responsibly. According to the ATF:

"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."