Spud Gun FAQ
Many of you have been asking if I still use my spudguns. No, I do not. I do not have the time, and I live in Chicago now, so finding an adequate and safe launching place isn't easy. The following is a list of frequently asked questions regarding spudguns and potato cannons.
What is a potato cannon or spudgun?
What are they made of?
Are they dangerous?
What are the legal implications?
How easy is it to build one?
What does it cost to build one?
What is a combustion launcher?
What is a pneumatic launcher?
What are the advantages to each?
Can I use DWV pipe or cellulose, even though it says not for pressure?
What does PVC stand for?
How does PVC differ from ABS? Which is better?
No one knows who started them. Legend states they originated from tennis ball cannons made from pop cans and lighter fluid, back in the 50's. They come by many names, spudzookas, PVC mortars, potato guns, spudguns, potato cannons. But they are all the same thing: an array of plastic pipe which propels a projectile, usually a potato, at incredible speeds, by means of combusted gas or compressed air. They can also be used for more practicle purposes, i.e. line throwing.
Spudguns are made out of Schedule 40 PVC pipe, the plumbers standard. They are NEVER CONSTRUCTED from DWV (drain, waste, vent) pipe as it is not meant for pressure and the resulting effects if pressurized could be deadly. It is thick and durable and has a great pressure rating to around 300 psi, so it is safe for minor 100 psi launches. Another method of construction is using ABS pipe, another durable type. I do all my shopping at the Home Depot. They have an excellent selection of every kind of pipe and connector, and their prices are very inexpensive. Radio Shack supplies all the electronics. Valves and hose clamps (for support) can be found at auto stores.
Like anything device created to launch something, spudguns are dangerous. They propel projectiles at high velocity, and thus you don't want to get hit by one or point them at windows or other important things such as cats. And when you shoot things like ice or wood as opposed to potatoes, they have much more mass and become even more dangerous, considering they do not vaporize on contact.
Combustion cannons use a flammable propellant and thus have a danger of exploding or fire, however this is rare if proper methods are used. Compressed air guns can be regulated to within the limits of the PVC pressure rating but still risk rupture or blown valves, however the usual pressure of 100 psi is well within the limits of the pipe. Combustion cannons can send the endcap of the pipe shooting off, and they can shoot large flames from the barrel. But they are generally safe when used with precaution and common sense.
Legality is a sketchy issue. All seem to agree they are novelty devices, for
amusement only. For all intents and purposes, they are a recreational device
which shoots small projectiles at stationary targets. Obviosuly you don't want
to go shooting small rodents out, or billiard balls at billboards, but for the
most part there shouldn't be a problem. Combustion cannons may cause a noise
problem however. I advise you check with your state and local law enforcement
agency for further information. The following is a letter that finds its way
onto most spudgun sites about legality. I can not vouch for its validity, however.
DEPARTMENT OF THE TREASURYMr. XXXXXXXXX
Bureau of Alcohol, Tobacco and Firearms
Washington, DC 20226
Sep 12 1995 3311.4
City, State Zip
Dear Mr. XXXXXXXXX
This refers to your letter of August 18, 1995, in which you ask about the legality of a device known as the "Spud Gun."
These subject devices are generally constructed from PVC tubing and fittings and are designed to launch a muzzle loaded potato using aerosol hair spray or other type of propellant. Ignition is by means of some type of "spark" igniter.
The Bureau has previously examined devices known as "Spud Guns, Potato Guns, or Spudzookas" and have determined that such devices, in and of themselves, are not firearms as defined in Title 18 United States Code (U.S.C.), Chapter 44, S 921(a)(3) or 26 U.S.C., Chapter 53, S 5845.
However, any similar devices which can be determined to be weapons by reason of their design construction, intended use, actual use, ammunition or other factors may meet the definition of a firearm under Title 18 or 26 U.S.C.
We suggest that you contact your State and local law enforcement authorities concerning possession of such devices.
We trust that the foregoing has been responsive to your inquiry. If we may be of further assistance please contact us.
Chief, Firearms Technology Branch
Building these can be fun, but the skill needed is advanced. You need a working knowledge of mechanics, hardware, construction and physics to know what you are doing, and it is good to know simple electronics for the triggers to some guns. Many young (16 or younger) people ask me about these, often for science projects, and I always advise them to consult an adult first. It's also a great bonding experience (hint hint you dads out there...)
Simple tools are all that is necessary. For more advanced guns, dremels or hacksaws may be necessary. Make sure to use proper ventilation when glueing and priming. Soldering electric components also takes some skill. Other launchers exist which are vastly more complicated, requiring more skill.
Building a cannon is a relatively inexpensive hobby. Most PVC pipe ranges from
$2 to $6 for 10 foot sections. Joints and connectors are around $0.39 to $4
for large pieces. Glue and primer are about $3 each. Valves run from around
$8 for good ball joints to $12 for electronic sprinkler valves and larger brass
ball valves. Electronics run around $12 for all the necessary switches and components.
All in all, expect to spend around $30 to $40 to make a good gun. Prices go
higher as the diameter and size of the gun increases.
|Int. Dia.||10'||90 deg. Elbow||45 deg. Elbow||Tee||Coupler||Endcap||Female Adapter||Male Adapter||Cleanout||Cleanout Plug|
Combustion cannons have a large chamber which reduces to a smaller diameter pipe, from which the potato is launched. Combustion is achieved by spraying in a propellant, usually hairspray. A flint or electric lantern igniter is used to generate a spark, which ignites the gases, propelling the potato, which can exit the barrel baked.
Pneumatic cannons are completely different, and thought of as much safer and more powerful. These cannons have two chambers, one in which air is compressed, and another in which the projectile is shot. Between these two chambers is a diaphragm, or a valve of some sort. When the valve is opened or the diaphragm flexed, massive amounts of high pressure air force the potato out.
What are the advantages to each cannon?
|Pneumatic||More power; regulated pressure, won't accidentally explode or misfire.
Can shoot water, ice, paper, snow, and other objects; quiet.
|Expensive to build, complicated parts; long reload time, quiet.
Valves need maintainance and cleaing, some require batteries.
|Combustion||Ease of use, simple design, low cost; fast reload time.
Can make some cool fiery projectiles, loud.
|Dangerous, can burn things or people, misfires or doesn't fire occasionally, size can be a hinderance, loud.|
DWV pipe (drain, waste, vent) and cellulose pipe are both marked NOT FOR PRESSURE. This means DO NOT USE THEM OR PRESSURIZE THEM AT ALL. This topic came up in the mailing list. These pipes can tolerate no pressures and will explode if pressurized, causing great harm or death.
PVC stands for Polyvinyl Chloride. Here is a link to PVC pipe statistcs and its applications: PVC FAQ.
The debate continues as to which pipe is better. I personally use PVC; this is only because I have not tried ABS yet. I am told ABS is stronger and cheaper, but I suggest you do your own research.