This is certainly not my invention and these arent even pics or videos of my guns (I have 3 of them but these are all pics I found online) and I know there have been topics about them before but they are such an awesome way to spend a few hours both building and then blasting away with that I thought I would share in case some of you have not had the good fortune to have learned of this miracle of pvc before. There are many variations of the spud gun, this is the most basic of designs that works very well and can be built in a short amount of time for less than $40.



The basic concept:


Items needed to build: (do not try this with anything other than schedule 40 PVC! Some serious pressure is built and ABS pipe will shatter possible causing harm) most of this can be found at a plumbing supply store, big box stores often do not carry 4" PVC.

1) Propane grill push button ignitor and some electrical wire to connect it to the nails/screws

2) 4" PVC Cleanout With Plug

3) 4" PVC Coupling  

4) 4" X 1.5' PVC SCH40 Pipe

5) 4'' To 2" PVC Reducer Coupling

6) 2" X 4' PVC SCH40 Pipe

7) 2 Nails or long deck screws

8) PVC primer & cement

9) Basic hand tools

10) A rod or dowel long enough to push the spud into the barrel

11) Spuds (ammo) and propellant - anything from an aerosol can that is flammable will work but cheap hairspray seems to work the best for me.





Instructions:
Step 1 - Cut the PVC pipes with a hack saw to the appropriate lengths according to the diagram above. (Make sure the pipes are cleaned).

Step 2 - Hammer two nails or screw in 2 long deck screws across from each other into the 4" PVC pipe (Combustion Chamber) where shown so that the ends nearly touch (your spark from the piezo ignitor needs to arc here). Wrap the stripped ends of the igniter wire right below the head of the nail. Make sure the points of the nails are about a 1/4" away from each other inside the pipe. Push the igniter button to make sure that you see a spark inside the pipe.

Step 3 - Apply PVC primer then PVC cement to the ends of the pipes where shown while cementing all the pipes together - DO NOT cement the cleanout lid shut, you will be removing this lid to charge the chamber with propellant for each shot (see pic above).
Wait 24 Hours for the cement to dry before shooting (this is important).
While waiting you can chamfer the end of the barrel to make it easier to cut into the potato when loading, and tape up the ignitor into a position on the 4" pipe that is comfortable to press while holding the gun, and paint your gun or have it hydro dipped and attach optics if you like that sort of thing.



How To Use:

Shove a potato with a ramrod or a stick down to the end of the barrel, try to fill the entire circumference of the pipe with the potato, you want a tight fit. Spray your propellant into the combustion chamber for a quick second and quickly screw in the cleanout lid (less is better, too much propellant and you wont get a good burn). Aim the barrel downrange, push the ignitor button to shoot. If it doesnt fire you likely have too much fuel and not enough air, try opening the lid and blowing fresh air inside then do a shorter spray of fuel. I keep an old towel with me to wipe down the inside of the chamber after a few shots, it seems to help. You will also want to clean the threads of the cleanout and lid every so often, especially if using hairspray or they will gum up and get very difficult to open otherwise.

Much more info is available online including complete parts kits you can order and assemble as well as fully built guns. Google is your friend. Have Fun!!!

Nice spud launcher.

Who is the cutie in the yellow plaid shirt?

I dont know but she has piss poor trigger discipline.

Limes work really well too, we file the outside of the end of the barrel to about a 45deg chamfer.  That way when you ram the projectile it cuts to fit in the bore.

ETA: I also use a lantern striker for an igniter (just a flint and spark wheel on a rod) and put it through the clean out plug so it doesn't get sprayed with hairspray.

I was pretty into them about ten years ago but all I built were pneumatic ones. I even had a source for rifled tubing.  I broke the sound barrier with a spud then I decided I was fucking with stuff that had WAY to much pressure to be safe and gave it up.

Newspaper for wadding, gravel for shot, birds die.

You can also wrap a sock up in duct tape and shoot it out of a potato gun.

I'll have to try this.

Nice spud shooters.

My buddy and I built one in the 6th grade for a science project and got in trouble. I kept the spud gun for like three years and did a lot of really stupid shit with it. The day we built it after letting the PVC glue cure my friend was looking into the chamber trying to make sure the ignitor was still arching after assembly and the vapors from the glue ignited and shot a giant fireball into his face scorching his eyelashes off. We used to pin steel wool to the potatoes with 1" staples so they were like tracers at night. In the 8th grade me and a friend went to his dad's house to shoot guns and he wanted to bring the spud gun along to show to his dad. His dad thought it was neat and had never seen one fired, thought it was just some toy that the kids built. He told my friend to shoot it at his tool shed so he could see the impact, and I told him it probably wasn't a good idea. When it hit it blew a gaping hole through the plywood and covered everything in the shed in aerosolized mashed potatoes that smelled like Aquanet hairspray. Another time a kid in our neighborhood dared me to shoot him with a rolled up wet sock and I declined. He said the magic word (pussy) and walked out into the yard and faced away from me spread eagle. When the sock reached him it had halfway unrolled and wrapped around his stomach after impacting his back and left a horrible streaking bruise. They are definitely nothing to fuck with.

I've always wanted to build one. That, and a trebuchet.

Spud guns are fun. I really want to build one "all out" that uses propane as a fuel... it's pretty easy to get into dangerous territory there.

So far my biggest obstacles have been:

• Grill starters suck and usually take several clicks


• Hair spray gums up everything. Couldn't get starter fluid to light for some reason


• Ventilating the chamber to bring in fresh air after a shot

Modern day staring fluid sucks ass.

Had someone bring a double barrel propane spud gun with da beamz at the hometown shoot,  it was a blast . They are definitely fun to have if you have them.

When you get serious, go pneumatic with a oversized dump valve.  

I had one that I plumbed to run propane from one of the small camp cylinders and the biggest problem I had was getting the correct air:fuel ratio

A standard milk carton lid makes for better wadding..  I had to much free time a child and was some what of a spud gun expert.. I even had one that would shoot a harpoon. Incase you are wondering, yes the harpoon actually work,  and I can tell you for a fact it will penetrate the side of a mail jeep....I also made flaming projectiles, but incase your wondering, yes, they will catch the corn field on fire. I even made an exploding round once.......Just once

Lol. Go on...

Not sure if the statute of limitations is up yet, but I do have some stories lol

I was really into them.  I had your basic hairspray cannon, and then I graduated.  I built one that was propane injected with a stun gun ignition out of clear PVC.  When Spudtech was (might still be) in business, I bought a few rifled barrels from him.  I also bought one of his SUPAH+ valves.  It is a piston valve built inside of a tee.  The piston valve was vented (actuated) by a 1" sprinkler valve, that was vented by an air compressor blowgun.  I built a cannon with a chamber from 4 feet of 4" pvc and had a golf ball barrel for it.  It was shooting golf balls just under the speed of sound (Verified by math and chrono).  Potatoes weren't an option, they wouldn't make it out of the barrel whole.  You had to wear ear muffs to shoot it.

Lantern lighters work better than grill starters IMO.