A potato gun (also called a spud gun or potato cannon) is a homemade launcher that uses either compressed air or combustion to fire a potato or similar projectile out of a pipe barrel. These devices are built from common hardware store materials, primarily PVC pipe, and have been a popular DIY hobby project for decades. While they might sound like a joke, potato guns are surprisingly powerful and sit in a complicated legal gray area.
How a Potato Gun Works
Every potato gun has three basic components: a combustion chamber (or pressure chamber), a barrel, and an ignition or release mechanism. The chamber is typically a wider section of PVC pipe, usually around 4 inches in diameter, while the barrel is a narrower pipe, often 2 inches in diameter. A potato chunk is jammed into the barrel end, where it forms a tight seal against the pipe walls. That seal is what allows pressure to build behind the projectile before it launches.
There are two main types, and they work very differently.
Combustion Potato Guns
These are the classic backyard version. You spray a flammable aerosol, commonly hairspray or spray deodorant, into the sealed chamber for two to three seconds, then cap the end. A BBQ grill igniter or lantern sparker creates a spark inside the chamber. The spray ignites, the burning fuel creates rapidly expanding gases, and that pressure forces the potato down the barrel and out the end at high speed. The whole sequence from spark to launch happens in a fraction of a second.
Combustion models are simpler to build and require no special equipment beyond a piezoelectric igniter. The tradeoff is that they’re less consistent. The amount of fuel sprayed in, the air-to-fuel ratio, and even the humidity can all affect how much power each shot produces.
Pneumatic Potato Guns
Pneumatic versions use compressed air instead of combustion. A separate air tank is pressurized using a hand pump or compressor, then a valve releases that stored pressure all at once behind the projectile. These builds are more complex because they require an airtight pressure vessel and a fast-opening valve, but they offer more control and repeatable performance. You can dial in a specific pressure for each shot.
What Potato Guns Can Actually Do
People often underestimate these devices because the name sounds funny, but potato guns generate real force. Depending on the design, barrel length, and fuel or pressure used, a potato can leave the barrel fast enough to shatter wood, dent metal, or travel several hundred yards. Combustion models tend to produce more variable results, while well-built pneumatic launchers can be tuned for greater consistency and power.
The projectile itself matters too. A tightly fitting potato chunk creates a better seal and catches more of the expanding gas, which translates to higher speed. Loose-fitting projectiles waste pressure escaping around the sides.
Where the Idea Came From
The potato cannon traces its roots to the World War II-era Holman Projector, a shipboard anti-aircraft weapon that used steam pressure to launch grenades at low-flying planes. The earliest DIY versions were far simpler: hobbyists would drop chunks of dry ice into a tube sealed at one end, jam a projectile into the other end, and let the sublimating gas build enough pressure to fire it. From there, the concept evolved through decades of backyard tinkering into the combustion and pneumatic designs common today. Potato guns remain a hand-built hobby. There’s no real commercial market for them, so every one you see was assembled by the person who owns it.
Legal Status in the United States
This is where things get serious. Federal law defines a “destructive device” as any weapon that expels a projectile by the action of an explosive or other propellant and has a barrel bore larger than one-half inch in diameter. A standard potato gun barrel is 2 inches across, well over that threshold. Whether a particular potato gun meets the full legal definition depends on factors like the propellant type and how the device is used, but the dimensions alone put it in a category that federal regulators take seriously.
State and local laws vary widely. California has strict regulations on projectile-launching devices that can sweep potato guns into weapons classifications if they’re used in ways deemed dangerous. New Jersey classifies any device capable of launching a projectile as an illegal weapon unless it meets specific exemption criteria. Massachusetts allows some municipalities to ban homemade launchers outright through local ordinances. Texas, on the other hand, takes a more permissive approach to DIY projects like potato cannons.
The practical reality is that enforcement often comes down to context. Firing a potato gun on private rural land as a hobby project is treated very differently than bringing one to a public park. But possession alone can be enough to create legal problems in stricter jurisdictions, regardless of intent. If you’re considering building one, checking your specific state and local laws first is essential.
Safety Risks Worth Understanding
PVC pipe is the most common building material for potato guns, but it’s also the most dangerous component. PVC is not rated for pressure containment. When it fails, it doesn’t deform like metal. It shatters into sharp fragments. Chamber ruptures are the most common cause of serious injury with these devices, and they can happen without warning if the pipe has hairline cracks, has been weakened by sun exposure, or is subjected to higher-than-expected pressure.
Combustion models carry the additional risk of flashback, where flame travels back toward the fuel source, and unintended ignition from residual fuel vapor in the chamber. Burns and hearing damage from the concussive blast at close range are also real concerns. Even on the projectile side, a potato fired at high velocity is not harmless. It can cause bruising, fractures, or worse at close range.