A Staple Gun, Caulking Gun, And Four-Barrel Shotgun

In its native form, [Clint]’s K-441 is a caulking gun, able to apply silicones, resins, and liquid rubber from a reservoir with compressed air. It’s accurate, powerful, has a huge capacity, and looks strangely steampunk, even for caulking gun standards. This isn’t any normal caulking gun; this device was made from a staple gun. Oh, it also fires shotgun shells with the help of four rifled barrels.

This device that shoots lead, steel, and glue started off its life as an ordinary staple gun, with the usual 23lb pull you’ll find on these guns. By adding a few plates, hand-winding a spring, and milling a few parts, [Clint Westwood] turned this staple gun into a device that would shoot a single .410 bore shell. A practice round as far as shotguns go, but still a serious amount of punch.


With the idea of a shotgun from a staple gun on a roll, [Clint] continued the build by adding several more barrels, each of which are rifled. The barrel rifling tool is a hack unto itself, starting off with a steel rod, wrapped around a larger pipe and tacked into place. A drill bit was attached to this auger-like device, the barrel was mounted in a jig, and the cutter was slowly moved up and down the barrel. The results are impressive for something that was probably made with equipment from Harbor Freight, and with a little cleanup, [Clint] had a quartet of rifled barrels.

In its final shotgun form, the K-441 holds four .410 shells loaded up with birdshot or slugs. The barrel indexing is done manually, but this device does have a safety, so it has that going for it, I guess.

Videos below, and as with all our weapons builds, you’re welcome to complain in the comments about how fat and/or stupid Americans are, or how Satan himself could not come up with a device of such concentrated evil. You’re also welcome to ignore these comments. Guess which one we’re suggesting?

51 thoughts on “A Staple Gun, Caulking Gun, And Four-Barrel Shotgun

      1. All rifled ones are (45LC/.410 Taurus Judge or Leinads etc.).
        What is more interesting, as long as it can chamber and fire shotgun shells, even one with over half inch calibre with a fully rifled barrel(like Ithaca DeerSlayer III) does not count as a DD ;)

  1. That barrel broaching tool is really fantastic! Lots of cutting fluid, lots of patience, and very long internal cuts become possible for all sorts of linear-to-rotational applications, not just rifling. I can imagine a handbuilt pneumatic piston with locking lugs at either end of travel, made possible by rotation, so that the mechanism can lock into place when not under pressure, the way that a hydraulic system can.

    I’m also incredibly impressed by (and very disappointed that it isn’t documented!) the stamped and folded parts in this build that weren’t part of the original staple gun. I’d love to see the fixtures that are used for producing those parts!

  2. Is it 45LC/.410 gun or just 410 one?
    If second, then rifle is way to fast and deep.
    To avoid problems with ATF(SBS) or payin 200$ stamp, shallow and almost straight groves are enough(plus much easier/faster to make and don’t disturb shot pattern that much).

  3. I hate to bring this up, but we all know it was going to be brought up anyway. Does anyone here know the legal issues involved in making something like this? Even in the US I’m quite sure all firearms must be registered and you can’t build your own unless you’re a licensed gunsmith or pay a “maker’s fee” or something like that.

    1. In the US, you can manufacture any firearm you would be legally eligible to purchase, provided you don’t manufacture with the intent to sell. And even that last one is fuzzy, because I believe you actually can sell the thing, as long as you can prove that wasn’t your initial goal. If you do wind up selling it, you’re also required to give it a serial number so you can complete the transfer paperwork correctly.

      This is why the media frenzy over 3D printed guns a while back was so hilarious. Who wants a crappy plastic .22LR when they can have a steel shotgun? Neither one is illegal, as mystifying as that is to Europeans and gun-fearing Americans.

      1. The serial number thing is not legal mandate. It’s a gentleman’s agreement between licensed gun manufacturers and BATFE. There are unserialized antique firearms that are bought, sold, and traded all the time and they are not serialized. Likewise, if you manufacture a firearm for your own, personal use and later choose to sell if off, you’re not required to serialize it, as you are still not a firearms manufacturer.

      2. “Neither one is illegal, as mystifying as that is to Europeans and gun-fearing Americans.”

        There’s nothing mystifying about that.

        The real debate is with people who think that 3D printing, or being able to make a zipgun in your garage, somehow defeats the gun control argument, which is that reducing the legal supply of guns and monitoring the guns themselves to reduce availability of guns and ammunition to criminals causes fewer criminals to carry guns because they become too expensive to obtain.

        They want to argue that because everyone can theoretically make a gun, they will, therefore gun control would only strip lawful citizens of their means of self-protection while the criminals would continue to carry homemade guns.

        Why don’t criminals in gun-controlling countries use these “liberators” all the time then? Because they’re really too crappy or too dangerous to use, or too time-consuming and difficult to make, and the punishments over being found with an illegally manufactured or obtained gun are too severe – in other words: guns are too expensive for the common criminal in many different ways.

        The rest of the criminals, who could afford the guns, don’t need to rob people at gunpoint on the street or break into your homes. They’re not into petty crime in the first place.

        1. It is not everyone making guns that making firearms that defeats the avowed purpose of gun control laws. It is that criminals will make firearms. In Australia where this is very restrictive gun control the Bikies (bike gangs that control the drug trade) have started contracting out machinists to make them full auto SMG’s http://www.thefirearmblog.com/blog/2014/04/04/australian-motorcycle-gang-diy-firearms-surface/ . The same is basically true in the Philippines http://www.guns.com/2013/04/07/vice-shows-how-filipinos-make-bootleg-smith-wesson-38s/ . Same is true in India https://www.youtube.com/watch?v=Wu1bBWcau_k

          1. Thus proving the point about outlawing guns or any other type of weapon. Outlaws will have them anyway and they will use them against law abiding people that have been stripped of not only the ability but the right to defend themselves.

          2. They’re FAR more likely to use them against other outlaws, informants, and Law enforcement. I’m sure John Q. Public does get caught in the cross fire though.

    2. In some states there is registration. In mine, there is no legal mechanism for registration of any firearm; you couldn’t do it if you wanted to. I don’t even think there’s any kind of licensing for gunsmiths. If you make it yourself, there is no fee or requirement to inform anyone. You can’t make something you couldn’t legally buy, but this doesn’t get crosswise of any NFA restrictions.

  4. Nice zip gun, better than most you find on YouTube. But don’t diss the .410 slug. It’ll kill you just as dead as a cluster bomb. It’s roughly the same caliber as a 9mm, a tiny bit smaller than a .45 and a tiny bit bigger than the popular .40 cal pistol that many police officers carry. Check out the YouTube videos called The Little .410 That Could. The old guy does some surprising stuff that’ll make you respect that gun.

  5. “As with all our weapons builds, you’re welcome to complain in the comments about how fat and/or stupid Americans are, or how Satan himself could not come up with a device of such concentrated evil. You’re also welcome to ignore these comments. Guess which one we’re suggesting?”

    I think hackaday learnt the lesson from the last firearms post…
    Anyway, interesting (yet slightly peculiar) build!

      1. It’s because there is no “unknown and potentially world changing tech” involved. Like 3d printing. The hype over “everybody will be able to go to the hardware store and BUY a printer and then PRINT guns of any type doesn’t apply to heavily modified staple gun “shotguns”. Those are yawn inducing. But 3d printers could print *anything*, right? even 100 barrel guns. Think of the kids! Sky is falling! Give it some time, the hype will drop off once people realize that a ABS plastic gun actually isn’t a very good idea.

        1. 100 barrel guns? Like Metalstorm? Or would that be Plasticstorm?

          Seriously, I think you “nailed” it, hehe. I always got the feeling the folks responsible for 3D printed guns were trolling for controversy and publicity, more than building serious weapons. Coverage by HAD, while it is a relevant topic, also played into the trollery. Now that no 3D printing is involved and even the most ardent anti-gun people have had a chance to recently rant, all is fairly calm..

  6. Thanks HACKADAY! Keep em coming, It’s really good to see there are no liberty/responsibility hating comments on this post. That and this is a freaking amazing hack with the homemade barrel broach.

  7. Not to be the first one to leave a negative but FOR THE LOVE OF GOD when you first test fire a home made gun DON’T HOLD IN IN YOUR F**KING HANDS, well unless you have a spare set at home. Also it looks like a bitch to fire with a 23 lb trigger pull, could that be reduced or if not how about attaching a front grip to steady the thing.

    1. What? I keep at least 2 spare sets of hands on hand at all times!

      ….but putting them on when I’ve lost my hands is rather difficult….

      gotta hand it to you, you’ve handed me quite a handful with that off-hand comment…. but for now, I wash my hands of it

  8. The ergonomics of the grip are back-asswards. For the next one, flip the staple gun around so the grip is properly angled and the fingers squeeze the trigger.

    How to get the firing system moving the right way? Well, that’s what hack(saw)ing is for!

    1. You’re absolutely correct on the ergonomics. It was even worse before I cut and moves the “trigger” forward. It was one big squeeze. The point of this build was simply to explore the limits of what could be done with a recognizable tool (staple gun). I didn’t document the background testing on the barrels and other safety features. I value my hands as much as the next guy. The Kevlar gloves and caulking BS was just some tongue in cheek humor that sometimes only I understand:)

      The upper and barrel assembly are being converted at the moment to drop onto a homebuilt FCG that has a proper grip and trigger placing. I’m using more hardware stuff like rod ends and door hardware. It will be a quick two bolt process to move back and forth between the two setups.

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