I suppose spud guns are firearms, right?


July 6, 2006, 06:32 PM
For the basic aquanet cannon with a 1.5" barrel, what volume ratio do you want to have between the fuel chamber and the barrel? I seem to remember being told a rule of thumb, but I don't remember what it is.


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July 6, 2006, 06:40 PM
The chamber should be 1.5 times the volume of the barrel

# Volume = Pi x radius sq. x length--(in inches)
# Example: 12" piece of 4" ID pipe.
# 3.14 x 2 x 2 x 12 = 150.72 cubic inches of volume

Schedule 40 PVC

July 6, 2006, 06:46 PM
If I understand correctly a " spud cannon " can go from a hobby to an Any Other". classification quickly depending if and to whom it comes to notice to in the atf structure LOL . but for only research uses ( not to build ) the previous posters have covered it imho

July 6, 2006, 06:47 PM
I made several with 12" PVC combustion chamber (3" dia.), necked down to a 36" barrel (1.5" dia.). The hardest thing to do is to wait 24 hours for the PVC cement to cure! Make sure you do it though! Otherwise you risk eating pipe fragments! Have fun!

Deer Hunter
July 6, 2006, 06:50 PM
My dad's old 'tater gun has a huge tube on it. I think it's a 4 caliber, hehe. It's a 4" tube that's around 6 feet long. I don't know how to make them, but he did kill a squirrel once with it.

July 6, 2006, 06:58 PM
If I understand correctly a " spud cannon " can go from a hobby to an Any Other". classification quickly depending if and to whom it comes to notice to in the atf structure LOL I think he meant as far as posting here on THR (ie keeping things firearms related)but...as long as you only launch potatoes you shouldn't have a problem...(bold emphisis added by me)

Department of the Treasury
Bureau of Alcohol, Tobacco, and Firearms
Washington, DC 20226

As defined in section 921(a) (3) of Title 18, United States Code (USC) the term "firearm" means --

* (A) any weapon (including a starter gun) which will or is designed to or may readily be converted to expel a projectile by the action of an explosive;
* (B) the frame or receiver of any such weapon;
* (C) any firearm muffler or firearm silencer; or
* (D) any destructive device. Such term does not include an antique firearm.

As defined in 26 USC subsection 5845(f) (2) the term destructive device includes any type of weapon by whatever name known which will, or which may readily be converted to, expel a projectile by the action of an explosive or other propellent, the barrel or barrels of which have a bore of more than one-half inch in diameter, except a shotgun or shotgun shell which the Secretary or his delegate finds is generally recognized as particularly suitable for sporting purposes; and (3) any combination of parts either designed or intended for use in converting any device into a destructive device as defined in subparagraphs (1) and (2) and from which a destructive device may be readily assembled. The term 'destructive device' shall not include any device which is neither designed nor redesigned for use as a weapon; any device, although originally designed for use as a weapon, which is redesigned for use as a signaling, pyrotechnic, line throwing, safety, or similar device; surplus ordnance sold, loaned, or given by the Secretary of the Army pursuant to the provisions of section 4684(2), 4685, or 4686 of title 10 of the USC; or any other device which the Secretary of the Treasury or his delegate finds is not likely to be used as a weapon, or is an antique or is a rifle which the owner intends to use solely for sporting purposes.

It is unlawful for anyone to make or possess a destructive device which is not registered in accordance with the provisions of the National Firearms Act.

We have previously examined that certain muzzle loading devices known as "potato guns." These potato guns are constructed from PVC plastic tubing. They use hair spray or a similar aerosol substance for a propellant, and have some type of spark ignitor. We have determined that these devices, as described, are not firearms provided that they are used solely for launching potatoes for recreational purposes. However, any such devices which are used as weapons or used to launch other forms of projectiles may be firearms and destructive devices as defined.

Bureau of Alcohol, Tobacco, and Firearms
Firearms Technology Branch, Room 6450
650 Massachusetts Avenue NW
Washington, DC 20226

Sincerely yours,


Curtis H. A. Bartlett Acting Chief, Firearms Technology Branchhttp://www.spudtech.com/content.asp?id=13

July 6, 2006, 07:05 PM
Since it's getting to be later on in the summer, I feel it's only my duty to mention that fresh corn on the cob (without the husk, of course) also makes for AWESOME launching from the 1.5" barrel.:evil:

July 6, 2006, 07:07 PM

July 6, 2006, 07:16 PM
When spud guns are outlawed....


July 6, 2006, 07:17 PM
Just don't go making spud warheads that detonate on impact, and you will be fine :D

July 6, 2006, 07:20 PM
You mean like a small prescription bottle filled with a bit of gunpowder and topped with a primer? :evil:

I could never get my combustion spudguns to light reliably every time, but I've had great success with pneumatic models.

July 6, 2006, 07:56 PM
Regardless of how many folks do it, do _not_ use PVC for something like this. It grows more brittle every time it's subjected to shock, pressure, many chemicals, and cold weather. Same reason it's not allowed to be used for air lines in shops or factories. Instant frag grenade.

By the way, skip the Aqua-Net and just use the propellant. Much less messy. IIRC it's either butane or propane.

But the best spud guns are compressed air.

July 6, 2006, 09:22 PM
i blew up my schedule 40 cannon am gonna go schedule 80
i've used propane and mapp gas use stun gun igniter works great but i'm guilty of overkill. 5 foot long six inch cha,mer 10 foot 2 inch barrel kinda like shooting plus p's from a deringer but fun to watch

July 6, 2006, 09:43 PM
Schedule 40 PVC should be fine, as long as it has a pressure (PSI) rating printed on it. I used schedule 40 for a mean little propane spud gun I made as part of a college project :evil:

As far as the ratios go, you want a 1:1 to 1.5:1 combustion chamber to barrel ratio. You should be safe with that.

July 6, 2006, 11:53 PM
The pressure ratings are water pressure. I'm not kidding, people have been killed by exploding PVC pipe. Even the heavy stuff.

July 7, 2006, 12:05 AM
Almost everybody uses PVC to make their spud guns.

It's cheap, readily available, and explosions are few and far between.

Even so, I err on the side of caution. Whenever I use the gun, I don protective eyewear, Kevlar vest, and I wrap the air tank (mine is pneumatic) in an old pair of denim jeans.

PVC is also weakened by UV light, so don't store it outside with the sun. It would probably be best to rebuild the gun every few months, just to be sure.

July 7, 2006, 12:50 AM
I always wanted to make one from metal piping that would use propane and fire a 12 oz soda can. I think a spark plug attached to a car battery would make the best igniter.

July 7, 2006, 12:56 AM
Strange... I've always read and been told that ABS pipe is the way to go, and to stay far away from PVC, for just the reasons previous posters have pointed out.

July 7, 2006, 01:45 AM
I went with PVC because I had trouble finding ABS locally. My main spudder at home is ABS and has many bags of potatoes through it. I don't like the PVC because it's much heavier. I also remember the pvc pipes in my father's house that are so brittle they break if you just bump them. I plan to wrap it in some duct tape and paint it to keep the sun off, then retire it early.

You can actually see the flame from just the latern lighter through the PVC. Cool, but freaky.

July 7, 2006, 01:47 AM
FWIW, PVC is extremely carcinogenic (cancerous growths have been noted within months) when inside the body, and doesn't show up on X-ray photographs, so is very hard to find and remove. Think of that when you're thinking "maybe a bit more fuel would be okay...." :)

July 7, 2006, 09:13 AM
I stick with air pressure these days, though I've made a pile of combustion cannons in the past. When you get tired of scrubbing tater starch out of your barrel and chamber, keep in mind that 2.5" PVC electrical conduit fits tennis balls perfectly. I have a large quantity of golf balls (my nephew lives right next to a driving range and we get pelted routinely) but I haven't found an over-the-counter pipe that fits them. 1.5" SDR21 PVC is supposed to fit them, but it's not available in my area unless I want to order a pallet of it.

July 7, 2006, 10:20 AM
If you run out of hair spray, and potatoes. DO NOT use brake cleaner, and a spark plug wrapped in duct tape. This will can hangfire and pass through both windows of a city bus, causing the police to increase patrol in your neighborhood looking for the shooter.

Matt G
July 7, 2006, 10:53 AM
I used Schedule 80 grey pipe for mine, and had to go to a specialty shop to find it. I felt a LOT better about using it than the standard Schedule 20 or 40 white pipe at the home improvement shop. For one thing, the white pipe breaks down under UV light when exposed to sunlight.

I didn't pay attention to ratios when I built mine, and probably should have. I did make sure that my chamber was very, very large, and worked my way up with timed sprays of hairspray. I eventually got about 200 yards with a decent spud.

All Set or Final Net hairspray worked pretty well, but I got tired of the whole thing after awhile.

July 7, 2006, 10:54 AM
If you go with PVC, do what others have said and get SCH40 or better pipe. Make sure the fittings are also pressure rated.

Our experience has been that lantern lighters work better than barbecue ones.

AquaNet is our hairspray of choice.


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