# DO NOT Build A Fully Automatic Battery-launching Air Gun

There’s nothing quite like [Elliot]’s cherubic sense of wonder and maniacal laughter after he tests his fully automatic AA battery-launching air gun. That fires 600 rounds a minute. At 200 feet per second.

We need to take a minute and say [Elliot]’s gun is stupidly unsafe. He used PVC pipe to hold air pressure, so that may… explode one of these days. Also, the AA batteries coming out of the end of the barrel have the same kinetic energy as a .22 rifle bullet.

The mechanics of the gun is a simple blow forward bolt. When he pulls the trigger, the bolt – and battery – are forced forward due to air pressure. After the bolt has cleared a plug, air is allowed to flow through the bolt pushing the battery along with it. Once the pressure in the barrel is back down to normal, a spring forces the bolt back into place and the 23 round magazine loads another battery. Simple, really. [Elliot] posted some pics of his gun on the spudfiles.com forum.

The gun is accurate to about 100 yards. It’s a very impressive piece of engineering for a bit of PVC pipe, but we don’t feel the need to copy this one. Check out the videos after the break to see this thing in action.

## 178 thoughts on “DO NOT Build A Fully Automatic Battery-launching Air Gun”

1. loans says:

This could be answered by the videos but I’m unable to.watch at the moment. My question is, HOW accurate at 100 yards? It must be like artillery, at 200fps.

1. loans:

Depends on the ballistic coefficient of a AA battery (probably pretty terrible), but yeah, my calculations show about point of impact to be almost 1000 inches below point of aim at 100 yards.

(Note: I assumed that AA batteries have a terrible BC of 0.01, because I can’t imagine them being very aerodynamic. If someone wants to work out the actual BC of AAs, I’d be happy to revise.)

2. John Boheman says:

Using your philosophy, a .50 cal Barrett is ‘inaccurate’ at a mile, since the bullet drops quite a bit at that range. ‘Accuracy’ has nothing to do with calculated drop of the projecticle … all you have to do is factor in how much drop you’re dealing with at a specific range. As far as BC goes, I would imagine BC is relatively negligle at 200 fps compared with the weight of the projecticle (a AA battery). My hat’s off to him due to his ingenuity and ability to improvise.

3. democratsarefascists says:

Substitute metal pipe, interior metal sleeve or ABS and it would be perfect, and more accurate. With metal and the right tool, you could even rifle the barrel interior without compromising its integrity.

2. anonymous says:

Jizzed in my pants

3. Max says:

AA batteries? Kind of weird. He should use a smaller barrels and twisted nails with the head cut off. Probably way more lethal and the exit velocity would have been higher with the smaller barrel size. And using PVC at high pressure is stupid.

1. Wm_Atl says:

80 psi is not that high for PVC. I have seen ratings from 280 PSI to 400 PSI on schedule 40 PVC. It appears he is using a regulator for the input into the PVC so he should be inside the safe operating zone, as far as pressure is concerned.

1. Besides, if you do feel the need to, ahem, ignore the “Do not try this at home” warning, it wouldn’t be all that difficult to substitute a C02 tank for a paint ball gun. After the tank is empty, one could refill it with air. Using stronger pipe for the structural pieces would allow for much higher pressure and better range. Longer barrel would increase accuracy, and using AAAA batteries, like those found in 9v batteries, would make for even more dangerous ammunition. All in all, not bad for an impromptu zombie defense weapon.

2. blB says:

Since when is using PVC well below the max psi rating stupid?

1. rj says:

since the discovery of material fatigue. Not to mention by drilling holes and cutting out notches, he is greatly reducing the strength of the pvc.

2. dimitri schreiber says:

well the psi for pvc is for a liquid, if the pipe cracks from a liquid, all that happens is it leaks and liquid flows out. gasses expand when they loose pressure

3. Dave says:

Or to negate the problem with PVC completely, use ABS plastic pipe instead. I used some pressure rated ABS to build my potato cannon.

ABS is designed to split instead of shattering, so even if you did have a failure, there would be almost no risk to your health.

4. fartface says:

Bah.

D batteries and crank it up to 200 PSI. the weight of alkaline D batteries going 400fps will knock over anyone wearing body armor.

4. nimitzbrood says:

I admire the man’s creativity but this is going to get him a visit from the ATF pronto. Anything full-auto that doesn’t shoot marshmallows or Nerf darts get the attention of law enforcement pretty darn quick. And in light of the fact that this can be pretty much built from off-the-shelf parts someone is probably going to be worried.

That said I’m damn impressed! I think if he dialed in the right pressure and timing he could easily do some real damage with this.

1. loans says:

Being that it isn’t a firearm, the ATF has very little to do with it. That is why you can purchase fully automatic BB guns.

1. nimitzbrood says:

I’ll buy that argument for the moment but honestly with what’s going on in the US right now I don’t think it’ll be too long before things that shoot anything will be restricted. Likely even paintball guns.

2. M4CGYV3R says:

They just passed Concealed Carry in my state, despite having not allowed it for the previous >150 years.

Guns aren’t going anywhere in the US. The corrupt politicians in charge like them too much.

3. M4CGYV3R says:

I want to see LED tracer rounds powered by the battery. That would be epic.

4. blB says:

That’s funny I thought it was the constitution that liked guns. Maybe corrupt politicians do to.

5. fartface says:

I can legally buy a fully automatic high rate of fire machine gun without a permit in the USA, as long as the gun was manufactured before 1986.

Problem is they are expensive as hell so only the ultra rich can own them.

but yes, if I had the cash I can go out and buy a RAMO M2 .50BMG With Mount machine gun, and the BATF cant do crap about it. that is a high rate of fire machine gun that throws .50bmg rounds. It would rip through any armored up Swat team like they were marshmallows covered in butter.

1. potato guy says:

if they shoot a rpg at you then you’re done.

2. Dre says:

Dude think a bit before posting shit like this… I have bought/sold/shot fully automatic paintball guns for over 10 years and I believe ATF has other things to worry about… And yes, rubber/plastic balls will do way more damage than those AAs…

1. nimitzbrood says:

*shrug* I call them as I see them and right now we’re one good famine away from a revolution here in the US where I live.

That brings up a good point – I didn’t see if this guy was in the US or not.

But yes I’ll check to see if my tinfoil is too tight. ^_^

3. Apothus says:

In Autralia.
Even having a basic version of this, im talking a single shot and have to repressure the tank before the next one is still classed as a firearm.

It can get you a visit from the police and some hevy fines & possible jail time.

Even paintball markers must be registed and you need a license to own one. I think you even need to proove to the police that it is stored in a gun safe.

1. Rawrl says:

Well, that’s ’cause it’s Australia, the same country that, for example, banned small breasts in pornography. It’s hardly a good benchmark for any sort of regulations.

2. raven says:

that’s illegal in almost every Europe Union country too, i think.

3. Legal ONLY in the USA is more correct than anything else.

4. ukilliheal says:

@nimitzbrood I have done some research, i have contacted the ATF, and my local sheriff. Both say the same thing: Its not illegal to have it, or even fire it as long as i don’t shot people, animals, or property(like cars, signs, windows …)

1. Crazytown says:

I’m not sure how you would fire small breasts at cars, signs, windows, etc. But I’d sure as hell like to watch her try

5. Andrew says:

Catastrophic failure of that device will be.. well.. catastrophic. I’d hate to be holding that when it blows. Otherwise quite impressive! If it ever gets rebuilt out of metal it’ll be scary (and lethal!)

1. randomdude says:

replace with steel – problem solved

2. ukilliheal says:

@Andrew If it makes you feel better i have done something that makes “catastrophic failure” less catastrophic. What i have done is welded together a jacket for the tank and barrel out of 80 geosynthetic membrane (the stuff they use to line landfills). Should either the tank or barrel explode the membrane will contain everything and safely vent the air though holes in the front.

1. ukilliheal says:

I meant to say 80 mil geosynthetic membrane

6. Quintin says:

I really don’t understand why you’d want to shoot batteries. Aren’t there cheaper and less polluting projectiles available?

Other than that; looks like a fun project to build. I think I’d be bored with the end result pretty quickly, though…

1. Ren says:

plentiful, cheap and heavy

2. nimitzbrood says:

Actually AA batteries are a pretty good ammo source.

1) The metal ones have some mass to them so do some damage when they hit. (The cardboard ones not so much but still would probably hurt someone/something.)

2) Plentiful. People throw out TONS of AA batteries daily.

3) Possible re-used of ammo. If the battery isn’t bent I can easily see reusing it.

4) They require no preparation to be used.

Not that aerodynamic but really this is a design that should be used for hopper-fed sentry guns anyway. Pair this with the motion detection webcam stuff people use for paintball guns and you could easily keep most things t bay provided you kept collecting used AAs.

7. Reg says:

Might want to modify the title by adding “out of PVC pipe”. I just hope it doesn’t blow up on him.

DOM steel tubing would be quite safe, but PVC shatters and w/ expanding air becomes shrapnel.

Same design using lead balls would be a potent weapon.

There are lots of articles about the hazards of using PVC pipe for air lines in a workshop.

8. jon says:

200 fps, 100 yard…
firing level at a target at 300 feet, at 200fps, the projectile would be air born for 1.5 seconds.
unless my math is off, gravity would put the projectile into the ground in about .5 seconds, even for very tall people.
While I can’t watch the videos at the moment, seems like the math is wrong some where, or it’s quite the arc to hit a target that far out… and that isn’t even taking into effect air resistance on an AA battery with a big flat surface on front…

1. anon says:

100 yards is the range from firing at a 45 degree angle.

9. Havel says:

That’s pretty darn awesome! Though for your sake, we all suggest using something other than PVC. I love how creative this is and would definitely want someone like him hanging around in the impending zombie apocalypse. lol
Nimitzbrood is right about the full auto thing. The launcher would be just as cool (and a bit more legal) with a bolt or semi-automatic action.
Keep it safe and keep it up! Good stuff.

10. hogg says:

Haven’t you ever built a potato gun? I can’t watch all the videos now so I don’t know if he states how much pressure is generated in his gun, but there are pressure-rated varieties of PVC pipe. IIRC, the pipe I used for my potato gun was rated for 280 psi. They use the stuff for water mains; it better not just explode one of these days.

That said, I’m not sure how the rating is done and whether it’s designed for rapid fluctuations in the pressure like that. The recipe I used for my potato guns dictated a duty cycle of at least a minute (mine was combustion-based and muzzle-loaded… how primitive).

And of course, the projectile is a little frightening, though I suppose it’s not much more dangerous than a potato gun or pumpkin trebuchet or the like.

Finally, I hope those glasses meet ANSI standards to protect his eyes while he’s shooting…

1. Dave says:

It’s the same PVC pipe, and it does fail under water pressure sometimes too- although in your house it’s more likely < 80psi so the chances are smaller. The biggest difference is potential energy stored in compressed gasses. Since water isn't compressible, a break in the pipe doesn't cause a catastrophic failure and release of energy resulting in shrapnel.

mumble mumble mumble high cycle stress fatigue mumble mumble

12. chango says:

The adult in me says “someone is going to win a Darwin award” while the child in me says “I wonder what would happen if you fired 18650s?”

Time to find some discarded laptop batteries…

13. orenbeck says:

Darwin Bats Last, and Karma’s his Pinch Hitter.

Seriously, the editor’s comment RE: Stupidly Dangerous, perhaps might be retired for the year! This may take the cake for producing a “Silent Keyboard” As in the Ham Radio abbv of SK

Back to .. this build. Oh, it’s truly impressive in the combination of workmanship and presentations.

ATF etc WILL be a quite real interested party if anyone actually builds such devices for other than perhaps a Zombie Movie Prop. As explanation of it’s reason to be at all.

All that said- This may also be tagged as an “Evolver” being as it could remove anyone around it from the gene pool just FOR being around it.

Don’t be Darwinbait, mnnkay?

14. scott says:

All issues with the PVC pipe aside, I can’t imagine a better “before” sequence in something advocating protective eye/head/body covering at close range. One hit on a particularly elastic part of the close up target and they’ll be pulling a AA cell out of some part of your anatomy.

15. Sniff says:

This is so dangerous to the user! I have blown PCV-pipe to bits in controlled environment and the pieces are not nice! I can’t recommend this project.
Second this is sooooo illegal in most of Europe!

1. Me says:

Many things are ‘so illegal’ in Europe ;)

2. Sharp pointy sticks are illegal in parts of Europe…

3. Pun says:

Wikipedia may soon be illegal in parts of Europe.

1. HomelyPoet says:

Butter knives are illegal in the UK, But not the families’ razor sharp Two-and-a-Half-hand broadsword.

“Who would like some roast lamb?”

4. ukilliheal says:

@Sniff I mentioned this above – but i built a jacket out of 80 mil geosynthetic membrane for the tank and barrel. This stuff will contain everything should the tank or barrel explode.

16. ferdie says:

i think this guy is a fan of the scrapheap challenge
from discovery channel. its make from bits of the trass its only time to get a explosion or the bold get stuk. i think only a american hill billy cam came up with this thing

17. grelfod says:

time for the gratuitous tree huger argument…
all those batteries being shot off like trash are hazardous waste oozing shit into the environment…
PVC pipe or Titanium won’t change that fact….

Now back to the drooling over the possibilities…

18. Having been in the room when an idiot friend fired a gobstopper out of a pistol style paint gun, I can only imagine a fully auto version could be quite painful. The gobstopper was fired at a solid wood door, it lost a few layers as it ricocheted and was quite painful even ~30ft from the door. Beware of idiot friends :)

1. Joe says:

Haha, so glad I don’t live with/near you or the video poster. (j/k) One of these days, that paintball gun he modified is going to split apart with enough force to impale someone. Hehe, cool device mod though.

The velocity of the gun isn’t really impressive since you could practically throw the batteries further, but that’s not the point. It is to see how common objects can be made into something awesome. And yes, the UK is ‘interesting’ about weapon laws. I’d be shocked if a rock(or AA-cell) in your hand isn’t considered just as bad as a knife or gun.

19. Hackerspacer says:

Oh joy, yet another unsafe PVC based projectile firing contraption. Using… PVC as the reserve air tank. Why do people insist on doing this? Because they see PVC can be rated at > ~150 PSI or so in water applications?

1. Because it’s cheap. The fact that there’s a pressure rating is just a bonus….

2. ukilliheal says:

Hackerspace, if your so worried about my tank being made of PVC, i could use my metal tank, but then the gun is no longer made of PVC – and its a lot heaver :)

1. Hackerspacer says:

/facepalm

Use whatever material you want to build yours out of. Just keep it away from me and anybody else for that matter.

20. Hackerspacer says:

What’s this noise about the ATF? This thing really isn’t anywhere close to being lethal aside from the risk of the PVC exploding / shattering. You can make and own cannons and flamethrowers and potato “cannons” and fully automatic paintball markers. On a scale of “items likely to cause death” – this doesn’t even register compared to most firearms you could drive to a store today and simply purchase.

1. kendon says:

yeah, this is not lethal… so you wouldn’t mind taking a full clip to the back of the head from six feet distance from this thing, right? if you still can say “not lethal” i’m convinced.

1. Colin says:

You have a point, but using the test of “would you like to take a round to the back of the head?” doesn’t really work. I really don’t think a round from a potato gun would kill you, but I still wouldn’t want to get one in the back of the head.

2. John says:

True, this could do some damage if you shot someone. But if I walked up to you and hit you with a baseball bat, it would do some damage, too. This think just isn’t that dangerous.

3. John says:

True, this could do some damage if you shot someone. But if I walked up to you and hit you with a baseball bat, it would do some damage, too. This think just isn’t that dangerous. At least, not to anybody but himself. Just say no to PVC!

4. HomelyPoet says:

He said the clip was about three or four pounds.
Sure, I’ll go first. I’ve taken heavier.
How tall ARE you, kendon, anyhow?

2. Blue Footed Booby says:

Why do people say things like this? Do they think laws are motivated entirely by what’s reasonable? Have they never seen a nonsense regulation that had an arbitrary cutoff between ‘legal’ and ‘felony’? Think about the Assault Weapon Ban, under which a given rifle may be legal with a wooden stock but illegal with a metal one, with no other changes.

There are many laws regulating firearms, and not all of them define ‘firearm’ to be something that uses explosives to drive a projectile. For some, it’s a matter of muzzle velocity. For others (particularly ones that involve using it to scare people) it’s purely up to whether the court decides a “reasonable person” would mistake it for a gun.

No matter how little sense it makes to you it would be a very good idea to actually *look up* the laws for your area before you build anything like this, and especially before you post videos on the internet. Even reading the law might not be enough because of how legal definitions work.

1. Dan says:

I’ll second that. In my area, this would be considered a firearm (specifically, a rifle, because it is longer than the 30″ or smaller definition of pistol/handgun). But the law here
states that anything that fires a projectile
through a barrel here is a firearm. They don’t really care if it’s fired with a rubber band, a spring, compressed gas, or chemical propellants.

On the other hand, rifles here are perfectly legal
to own, and do not have to be registered, although
fully automatic is quite illegal here without the proper licensing (which requires a yearly unnanounced visit from the ATF). In the event of zombie apocalypse, I’ll stick to my collection of real firearms, all the same..

Props to the builder, aside from everyone’s safety concerns, this thing is pretty ingenious, and my boss’ son wants me to build one for him. I refused, since the poor kid would probably shoot all of the computers in the office first, all of the cars and windows in the parking lot and neighboring businesses second.

21. carbinefreak says:

Well it actually looks like hes regulating the pressure down from tank level to something useful…. so yes its stupid to use PVC but its less stupid than running a couple hundred PSI in PVC. Epic build though

22. Timberwolf0122 says:

It’s not that dangerous from a PSI front the compressor will be at most 120PSI and the 1″ PVC has a working tolerance of 270PSI with a burst of 1440PSI (link to PVC lookup)

1. earl says:

Even though these PVC guns aren’t exceeding the pressure rating of the PVC, the ratings are probably calculated under a slow rise equally distributed over the entire length. A gun will have a sudden pressure applied over one area, then the pressure will ripple down the length. I’m no physicist, but I’m guessing the PVC isn’t rated for this type of uneven pressure waves that undoubtedly cause high speed flexing/waves whatever. I think guns like this are totally awesome, totally fun, but also probably dangerous, who knows. Have yer fun, life is short.

23. Hamtaro says:

Silly…

Couple notes:
The ATF can confiscate the launcher if they wanted to. The term firearm is loosely defined: (4) Any destructive device. Such term does not include an antique firearm.
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.
When queried about potato guns, the ATF responded: a spudgun was not a destructive device since it was designed and used solely for launching potatoes for recreational purposes. However, if launching other forms of projectiles, the device may be classified as a destructive device.

As a second aside, it is generally illegal for an unlicensed person to build a machine gun firearm unless it is for the state. And, a machine gun being defined as a firearm which fires more than one round per a pull of a trigger.

1. ukilliheal says:

Hamtaro… who gave you the idea that i am not licensed to build firearms?

1. HomelyPoet says:

The polyvinyl chloride, squealed on you.

24. Nick says:

I have a pneumatic that shoots golf balls over 700 yards at 180 PSI. SCH 40 has an operating pressure of 200 PSI and a burst pressure of over 600. With the assumption that the PVC is not exposed to UV light and the joints are properly cemented, it is only dangerous when you drop it with a charge, which I will admit I have done, it broke in two piece each flying to opposite sides of the shop.

1. Mizchief says:

Which is all reason enough not to use PVC for any type of pressure containment.

1. Nick says:

*facepalm* PVC is perfectly safe at the rated pressure, else they would not rate it to such pressure. Naturally it was designed to be stationary and buried but if proper considerations are made it is not unsafe, all the guns I make are blocked and strapped between the reservoir and barrel to minimize torque between joints. Even at 180PSI I can attest that had the device exploded next to my face I would have been partially deaf but otherwise unharmed. The device broke in 2 pieces which is common of a stress fracture versus a true explosion caused by brittle plastic/too much PSI.

25. arfink says:

80 PSI is nothing to worry about, even in PVC. You show me video footage of a PVC airtank exploding (not merely having an end cap pop off) under only 80 PSI and I’ll believe you.

1. Just proof that you’ve got to use your brain when you’re working with pvc and air.

If you’re only willing to work with technology that’s safe even if used carelessly you’ll miss out on a lot of the most interesting possibilities.

2. Marshkillz says:

in regards to the video. that’s about the worst design for a pneumatic gun I can imagine.. the 90 degree angle is both a pressure supporting piece and a mechanical supporting piece.

As for using PVC for Pneumatic devices, PVC is a perfectly fine material to use as-long as you use it well within its specifications and design the cannon accordingly.

The PVC in my cannon is rated at 300 Psi but I never charge it above 40 due to the mechanical shock of firing.

3. ukilliheal says:

I have had the same thing happen on a larger potato cannon. The joints failed. This is the only reason i am using steel pipe as the joins in my battery shooting air gun.

4. N0LKK says:

Glue/cement/weld the broken pieces back together than broken gun is as good as new. ;)

5. cmholm says:

@Marshkillz, running 40 psi within 300 psi pipe to handle discharge shock *sounds* reasonable, but a diy digital pressure sensor recorder would make for better test and validation, and offer an added, “socially redeeming” follow-on hack (the recorder, not the resulting better engineered battery/spud/marshmallow gun).

6. randomdude says:

That is DWV (drain waste vent) PVC – NOT a proper pressure rated PVC

I don’t understand why he didn’t use steel pipes and fittings

26. Mizchief says:

Please at least wear some shooting glasses if not full on safety goggles when using this thing. People like this get their eyes gouged out with PVC shrapnel, then need the government to pickup the tab a the emergency room, then pressure cannons become a felony ruining it for the rest of us.

27. me says:

In NJ, that would be a firearm and land this guy in a scenic apartment in camden along the delaware river for probably 20 years given its also automatic…

28. arfink says:

You’re just jealous you didn’t think of it first.

1. kendon says:

uhm yeah, no, not really. i’ve build my share of spudguns and stuff that shoots other stuff, but it never crossed my mind to use hazardous waste as ammunition.

29. maiden says:

He should shoot LiPo batteries instead :D Kaboom.

This thing is wrong in all ways i can think of.
1. its a gun
2. its badly designed (unsafe for the user)
3. shooting BATTERYS! what are you thinking! environment friendly?

1. Timberwolf0122 says:

I’ll give you 2 and 3 but being a gun is not a bad thing.

1. Amazed says:

unless you’re on the receiving end.

2. HomelyPoet says:

I’ll give you 2.
@Amazed
Been there, Done that, Even received the “T-shirt” for it.

30. disgustipated says:

tune in next week when we test fire mortar launcher which shoots lantern size 6v batteries

1. disgustipated says:

we shall call it acid rain

2. Tux says:

Roflmao….

31. Hirudinea says:

To all you PVC use crybabies, look at it this way, he’s going to be the coolest guy in the emergency room!

1. pbjamm says:

“Bones heal, chicks dig scars, and the United States of America has the best doctor-to-daredevil ratio in the world.” – Lance Murdoch

32. ironring says:

Two thoughts (and these may be elsewhere in the comments; I obviously have not read them all):

This first one may be a little mean, but here goes: Kinda depressing fat kid building fully automatic weapons with no regard for his own safety, testing them all alone without friends seems very disturbing, and I’m a little afraid for his community.

Second, this guy is blasting chemical-filled batteries (probably defunct, toxic rechargables) into hard objects likely to cause rupture all over his garage and backyard, let alone other places in his neighbourhood. Can any one say heavy-metal poisoning? If he’s got the know-how to build this gun, you’d think that he could use dowel cuttings or solid plastic rod (please, no solid metal; you’re dangerous enough already) instead?

1. sneakypoo says:

Not only is it mean, it is also incredibly narrow minded. Regardless of having friends or not, do they always have to be present whenever you dick around with your latest project?

2. Joe says:

Granted, it would make sense to have an assistant, you’re wrong about the AAs. Those are the kind that aren’t rechargable (Alkaline), aren’t legally allowed to have lead and mercury, and would end up in a landfill anyways. It said Rayovac Alkaline on the box, so you can tell what brand and type they are. It is a shame though, that billions of those batteries (cells) are essentially wasted instead of recycled into new ones.

I have one of those old Renewal rechargers and contrary to marketing, you don’t need alkalines designed for recharging to use it. Just don’t try it with Duracells. Hehe, I sat and tested different brands while doing something nearby. It’s the only brand that I couldn’t reuse. Taking apart a Duracell pretty much shows you why they don’t work if you have some chemistry knowledge.

There was a Popular Electronics article on recharging alkalines long before the Renewal chargers came out. Rayovac’s big innovation was that their charger recognized if it was charging NiCds or NiMHs as well.

Just remember, not all Alkaline Batteries are created equal. I have actually seen a house that started on fire because of the brand (Duracell) battery being used in the smoke alarm (First Alert).. Their version was slightly too big for the compartment and bulged to the point of no return

Consumer Reports story

2. joe says:

Who the heck uses Duracells in a smoke detector/fire alarm, anyways? The Energizer brand seems to have a longer life in low-drain devices from experience.

“, the recommended replacement batteries are the Eveready batteries”
Haha, figures…

The fact that the alarm was trying to charge the battery, is very likely what caused the battery to go like that. Think that’s scary? Try the sound that motherboards make when their capacitors go. It’s like a bag of popcorn with sharp flying pieces of aluminum instead of fluffy corn. :P

33. jordan says:

His laughter when he fires that thing is awesome :D It’s such a good feeling when homemade instruments of terror work so well

1. Joe says:

Why do I feel like making a Chrono Trigger reference? Lucca was exactly the same way! :)

34. Even taking high cycle failure into account, the pipe is much more likely to fail gracefully than explode into a puff of shrapnel.

The ‘explosion’ school of material failure falls under the heading of ‘fracture mechanics’. The basic idea is that the sides of a crack act as lever arms that concentrate stress at the tip of a crack. The tip itself acts as a fulcrum, and the material around the tip acts like a spring.

A crack can’t grow until the stress at its tip exceeds the rupture strength of the material, and the effective spring around the tip disperses stress away from the tip. The more ductile a material is, the more stress the spring can absorb before the stress at the tip of the crack gets high enough to make the crack grow.

A crack can’t fail catastrophically until its growth creates a positive feedback cycle.. making the crack longer makes the material weaker and the stress concentration from the sides of the crack higher. As it turns out, there’s something called the ‘critical crack length’ for catastrophic failure. Cracks below that length simply can’t get the positive feedback necessary to make the material go ‘pow’.

PVC pipe is designed for two failure modes: ‘bulge before break’ and ‘leak before break’.

The ‘bulge before break’ failure mode involves plastic deformation. You get what amounts to an aneurysm. The energy necessary to deform the PVC absorbs enough energy to keep the material from unzipping, and gives you an easily identifiable point of failure.

The ‘leak before break’ failure mode makes the critical crack length longer than the thickness of the pipe wall. Basically, it’s always easier to open a crack from the inside surface of the pipe to the outside surface than it is to make a crack grow along the surface.

In both cases, you’ll get a localized failure that’s easy to see long before you get an fast-moving ball of shards.

1. Jeremiah says:

very nice to see some knowledge here. PVC doesn’t shatter in the way that a grenade casing shatters. I’ve had PVC implements fail near me and the most I or any of my cohorts suffered was having the shiz scared out of us by the sound.

I’m not saying it’s safe under all circumstances, I’m saying it’s designed to fail safely in almost all circumstances.

35. Rosco says:

Has anyone posting here ever actually had PVC explode under pressure? I had a 2.5 inch mortar (firework) explode a PVC tube due to no lift charge. I was standing exactly 9 feet from it, and there were 8 spectators only 12-14 feet away. No one was harmed. It is far less eventful than you all make it sound. 100 PSI (or less) probably wouldn’t even penetrate his shirt… minor lacerations at best.

1. The video posted in the comments is pretty good example. Practically speaking, the only way it happens is with designs that (idiotically) put tons of torque on a joint. Do that and drop it and you’ve got an almost guaranteed failure.

2. Sorry about the non-sequitur response, I misread your post. That’s an interesting point besides. Someone should do some ballistics gel tests.

1. dan69 says:

id bet the batteries would bounce off ballistics gel

36. raidscsi says:

This man has value in any post apocalyptic society.

1. rasz says:

value as a food source maybe

1. kendon says:

yeah, only if he is not highly toxic by then from all the smashed batteries in his garage. cholesterol would probably be less of a concern post-apocalyptic.

37. Lummox says:

Sch40 PVC can handle 300 psi, and this guy has 2 layers of (unknown quality) pipe to go through. I wouldn’t be worried. Yes, I own multiple compressed air potato cannons.
If you want to make something like this that is ‘stressed to the limit’, wrap it in duct tape, more in high stress areas. If you want to be uber paranoid, double wrap thin nylon webbing material around it, then your favorite color of duct tape. You will catch (most) any shrapnel. Lighter than steel and easy to fabricate. Go with a sch40 pvc tank, plastic fittings and such. then you can take it through metal detectors :)
“Sir, what’s that large tube hanging out of your pants?”
“Why, i’m just happy to see you, officer”

Ok, I always use copper or steel fittings. Think reliability. If you rifle your barrel it also becomes weaker. Remember that.

*Disclaimer* Don’t be an idiot. Do you trust everything you read in the internet?

And find some better ammunition already. This is more environmentally unfriendly then my (all steel) hello kitty liquid propane flame thrower .

38. rasz says:

I was about to make the same comment

39. Bob says:

I’m with the many posters above, the choice of projectile is thoughtless (the use pf PVC has been noted). Not optimal by projectile standards not to mention the environmental implications. Given all the effort I’ve spent carefully saving all my dead batteries for proper disposal/recycling, this kind of makes me cringe to watch.

1. HomelyPoet says:

I prefer to harvest the elements of the batteries for…Hrm, never-you-mind-why.

40. What’s interesting to note is that not all batteries are the same. With wildly different densities/chemical makeups, etc. Some contain lead, others contain lithium, etc…

So when you give accuracy up to x-yard ratings, without any specification of what kind of batteries he’s using… well that’s ass.

Lead/Acid at a high enough velocity/accuracy could potentially be more deadly than regular bullets (not necessarily hollow-point, etc…)

Every time these high-pressure PVC projects come up, I wonder if there might be some way to re-inforce them to increase the safety factor. Certainly PVC is cheap and easy to build with (i.e. no machine shop needed).

Perhaps a fiberglass sheath would help? I’d imagine even an un-resin-impregnated nylon bag sewn around the PVC parts would seriously increase safety, if nothing else to cut down on the shrapnel when it blows.

1. PJ Allen says:

I was wondering about reinforcement, too. Maybe wrapping it with wire, like a multi-layer air-core coil.

2. therian says:

people wrap spud guns with towel, if it blow up than at leash sharp pieces get caught in cloth

3. therian says:

tree hungers stop it already, people trow out ton of batteries daily, this guyamount of pollution is like grain of sand on the beach

1. therian says:

strange, this comment end up as reply when it wasn’t

42. therian says:

I build a single shoot AA rifle in HS, too bad I leave it in wed basement and now it rotten

43. NotImpressed says:

Wow… redefining “neck beard”.
That guy needs to get out of the house some more…

44. grovenstien says:

This is full of Win and Epic fail all at the same time. Politics, ethics and morals put to one side, this is great build.

45. sungod says:

Use AAA batteries instead, then you could also use Nerf bullets (Same Size). They make AA -> AAA battery adapters so you could change your entire house over to AAA and have Tons of Ammo. Make a Cardboard Handle and Stock and wrap the Entire thing in 5 or TEN LAYERS of Fiberglass and Resin.

I LOVE the idea to use Pop cans instead. It would make recycling a fun day. Paint ball filled Pop can Shotgun shells anyone. NO, how about Mortar shaped pop can artillery shells.

Huge Gun , Huge Clips (or Belt driven), Fiberglass & Bondo Grip and Stock all covered up, Pop cans with wax paper whistles inside to make them scream as you shoot
= Future Juggernaut Gun

46. therian says:

when I was playing with spud guns I had an idea to use liquid fuel instead of compressed air, in theory you can create chamber where you heat alcohol or like fuel and turn it into vapor than ignite it with a spark. Newer realize this idea thought

47. Lemonmaster0 says:

Wow. Alright, anyone that thinks that this is even remotely illegal in the eyes of the ATF doesn’t have any idea what they’re talking about. Also, I don’t believe for a second that it has the same kinetic energy as a .22. A .22LR round has an approximate velocity of 1,640 ft/s for a 32gr projectile which is about 259 J. A AA battery at 200 ft/s only has about 42.7 J. Please do some research before posting incorrect data and spreading stupidity. I DO, however, agree that this is still unsafe.

1. No One says:

Math correction:
32 grains * (1640 ft/s)^2 = 518 J
22 grams * (200 ft/s)^2 = 82 J

1. No One says:

Ahem. I missed a factor of two in my math correction! Oops. Your math stands!

2. SOI Sentinel says:

Your units do not match. Did you convert grains to grams first? So, it’s more like this:

32 grains = 2.07 grams. Now, KE= 0.5* M*v^2

22lr = 0.5*0.00207kg*(500m/s)^2=259J
AA = 0.5*0.032kg* (61m/s)^2=63.4J

The ratio is less than 5:1 instead of 10:1. As a comparison to the “usual” HaD firearms projects, this is still a lot more energy than most have put into projectiles of a coilgun. Then again, most of those are powered by a few AA’s, not firing them.

3. SOI Sentinel says:

Ack, nevermind, got my battery mass wrong.

48. Alex says:

I want to be indignant about how unsafe this is, but it’s just way too awesome.

49. Lemonmaster0 says:

That is a point. It is still a cool design.

50. That thing is a riot.

Batteries probably aren’t a great idea, but I’d guess the PVC is fine. Sounds like he’s already working on alternative ammo… so folks here can take the righteous condemnation down a notch.

Fun videos, thanks for sharing. Try to be safe, and don’t leave ‘dem batteries in the park. :D

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