tater guns

[JohnYayas]

As for how to build one, it's super easy. You need the following parts: ...

Thanks for the detailed write up, Adam. I think I am going to give it a shot with your plans. I think I have most of the stuff laying around the house so why not?

[sugeek]

Thanks for the detailed write up, Adam. I think I am going to give it a shot with your plans. I think I have most of the stuff laying around the house so why not?

Don't use PVC it can shatter, use abs pipe. PVC is fine for the air compressor spud guns.

Propane oxygen (mapp gas torch integrated) was the best spud gun we built had a 400 yard range at its best.

The compressed air ones could probably meet its performance.

Adam

[DrEvil]

When I was a kid (15 or 16) I made one from some old cast iron piping I found lying around.
I drilled a hole for a spark plug and fitted a propane feed.

It was great fun. However the local Police Firearms officer confiscated it after a day or so of my playing with it in the fields out the back of my house.

He later told me he wasn't officially allowed to do so as technically it wasn't classed as a firearm... however, during testing at their range they managed to put a King Edward through both front doors of a Ford Fiesta at around 100 yards, hence he wasn't giving it me back.

He also said I was lucky it hadn't exploded in my face...

How the heck does a potato go through that much metal? That seems fishy to me. I would guess it went through the glass or the windows were down.

[araugh]

Built one for a kid's birthday party a few years ago, since it was for use around kids I went with compressed air instead of combustion. Designed a cocentric launcher, the barrel is 1.5" schedule 40 seated inside of 4" schedule 40 PVC with a piston valve. When air dumps from behind the piston the pressure differential pushes the piston back from the barrel and the compressed air rushes into and out of the barrel. It's a great design, nice and compact and even at just 40PSI it launches jumbo marshmallows over 100 feet. When the kids weren't around we cranked it up to 100PSI and got 350 feet regularly. Jumbo marshmallows are pretty much the perfect ammo since they squish to fill the barrel perfectly like a sabot and there's no wasted pressure leaking around them during launch. The ball valve on the back was too slow for optimal operations and has since been replaced with a modified sprinkler valve. Here's a video of it shooting 7 marshmallows at once at 40psi

http://www.youtube.com/watch?v=VxmJra4Eo2Q

[JohnYayas]

Built one for a kid's birthday party a few years ago, since it was for use around kids I went with compressed air instead of combustion. Designed a cocentric launcher, the barrel is 1.5" schedule 40 seated inside of 4" schedule 40 PVC with a piston valve. When air dumps from behind the piston the pressure differential pushes the piston back from the barrel and the compressed air rushes into and out of the barrel. It's a great design, nice and compact and even at just 40PSI it launches jumbo marshmallows over 100 feet. When the kids weren't around we cranked it up to 100PSI and got 350 feet regularly. Jumbo marshmallows are pretty much the perfect ammo since they squish to fill the barrel perfectly like a sabot and there's no wasted pressure leaking around them during launch. The ball valve on the back was too slow for optimal operations and has since been replaced with a modified sprinkler valve. Here's a video of it shooting 7 marshmallows at once at 40psi

http://www.youtube.com/watch?v=VxmJra4Eo2Q

Stealth mode. Nice!

[buffo]

Don't use PVC it can shatter, use abs pipe.

So long as you don't start messing around with exotic fuels, schedule 40 PVC pipe has a 5-1 safety margin on over-pressure, and that's based on it's maximum WORKING pressure, which it's designed to hold indefinitely. I've never heard of one shattering when using hairspray or butane, except in the glactically-stupid cases where someone used DWV pipe instead of Schedule 40.

Now, if you start fooling around with MAP gas, Methane, or Acetylene, then you might just make a bomb, and in that case ABS is preferred. But I posted a warning about exotic fuels in my initial post.

ABS is much harder to source, and gluing it can be tricky. (Any idiot can glue PVC and make it work, but it is possible to screw up an ABS joint.)

I've actually installed a compression gauge on one of my cannons and fired it multiple times to measure the combustion chamber pressure. Normal readings are around 40-45 PSI, with exceptionally hot shots reaching 55-60 PSI. So there's no danger in using PVC so long as you use standard fuels. As I said above, I have a pair of cannons that are nearly 20 years old and still going strong.

Propane oxygen (mapp gas torch integrated) was the best spud gun we built had a 400 yard range at its best.

Instead of trying to increase the combustion chamber pressure by playing with exotic fuels, you're much better off simply making the barrel longer. A 2 ft barrel will loft a potato 150 yards on normal hairspray. Jump up to a 4 ft barrel with the same fuel, and you can more than double the range. And if you really want some fun, go with a 1 1/2 inch barrel instead of 2 inch. I've got one with a 5 ft barrel of 1 1/2 inc PVC, and I can routinely break 400 years with it.

Also, larger is not always better when it comes to the size of the combustion chamber. My cannon with the 2 inch barrel has a large combustion chamber (around 14 inches), but the one with the 1 1/2 inch barrel has a much smaller chamber (probably 8-9 inches) and it's a far better performing spud gun. I've seen them with chambers as short as 4 inches, and they still perform great.

The compressed air ones could probably meet its performance.

Compressed air cannons are vastly superior to the combustion designs. With 110 PSI and a 20 ft barrel, you can reach sonic velocities. There used to be a website that explained the math behind one of these (aptly named the BFPG-9000), but it's since been taken down.

Bottom line: Air cannons are far more powerful. But they are also more complex, and a great deal of their success (or failure) rides on how fast the dump valve can open. I've always wanted to build one, but it seems I've always got something else competing for my time...

Adam

[mixedgas]

One of my former employers has a letter on his wall from BATF certifying they do not consider his compressed air spud cannon a firearm.
He had to get it when the local gentry complained about the ~1200 foot range. Fortunately he has a very long farm.

Probably the only letter ever issued from BATF with "Be safe and have fun" as the closing statement.

Steve

[buffo]

When I built my first potato gun, I called the Dorchester County Sheriff and asked him to come out to see it. (He'd been out to my neighborhood several times to watch fireworks on the 4th of July and New Year's Eve. He was a cool guy.)

I asked him specifically if this was considered a weapon. His answer was quite enlightening:

"It is a toy, right up until you start to use it as a weapon. At that point, it becomes a weapon." He presented a baseball bat and a shovel as analogies. One is a toy, the other is a tool, yet both can become formidable bludgeoning weapons if your intent is to harm someone.

So the answer is: Potato guns are not specifically classed as weapons, but if you are caught using one in a manner that would appear to be either recklessly negligent or genuinely malicious, then it becomes a weapon in the eyes of the law.

Adam