You’ll shoot your eye out, another coilgun

All we needed to read was 4x 3900uF capacitor bank to know we had yet another decently sized homemade coilgun on our hands. And for the math buffs, that equates out to 1.25kJ of potential energy (efficiency kills it down to 37j of kinetic, but large numbers are more fun) which is more than enough to break skin; of course we recommend you just shoot old electronics rather than friends. On the more technical side, sure its only a single stage for now and we’ve seen some slightly more impressive triple stage guns, but it may just be more beautiful than our previously featured coil pistol. You guys be the judge. Catch a complete video after the jump of the internals and build process, skip ahead to 2:40 for the destruction.



  1. Brennan says:

    3900 uF? That’s like, 3.9 mF!!

  2. Drew says:

    Damn, that’s pretty.

  3. macona says:

    Neat, but a good slingshot has about as much damage capability as that does. I think I would have used a boost converter to charge though.

  4. jh says:

    I wanna mount one to each front fender for use in traffic *evil grin*

  5. strider_mt2k says:

    shuts jaw manually

    Time to kick ass and chew bubble gum…

  6. xeracy says:

    Anyone see this on several other websites over the past week? Usually its gizmodo and other sites finding out about stuff from HaD, not the other way around. Maybe i just spend too much time online…

  7. Zmaster says:

    Awesome building!

  8. Torvaun says:

    Looks awkward to hold with the capacitors there. I’d have gone with side of the barrel. Which would be awkwardly front-heavy, but at least it’s not getting in the way of your arm.

  9. jeditalian says:

    damn if you could only do away with the projectiles and fire a cutting laser (cutting your enemy in half)

  10. Amtal says:

    Rate of fire’s kinda low.

    How about an electrified bayonet to compensate?

  11. biozz says:

    i have 10 400V 3900UF caps i got off ebay for $5 a peace not doing anything … get my self some SCRs some enameled wire and maybe throw together a 4 stage? (one for injecting) may be fun .. but a can crusher is slightly more appealing to me … maybe a wire vaporizer … or maybe a rail gun or maybe *walks away rambling*

  12. biozz says:

    second post

    this guy needs a better charging circuit … maybe a large buckboost or a SMPS (although it may be a pain in the ass to wind the xfr)

  13. M4CGYV3R says:

    4x 3900uF? That’s over 9000!

  14. draeath says:

    Very slick presentation!

  15. Mike says:

    I have 300F caps here… too bad they are only 2.4V
    (yes, farad, as in 300,000,000uF). Also have some 5000F caps.. One of these days I’ll make an ultracap railgun..

  16. brad says:


    the cake is a lie.

  17. Vetter says:

    Show us what it’d do to a block of balistic gel.

  18. jg says:

    Is it just me, or does this guy remind you of Sid from toy story?

  19. biozz says:

    @M4CGYV3R actually id use all 10 and double up per stage
    thats 39000 XD … id need to get some hockypuck SCRs fro that … but i have seen bigger coil guns

  20. xrazorwirex says:

    I’m poor so I’ll just have to use about 50 of the low-capacitance 2100V caps I got lying around the shop. I’ll make the charging circuit out of TV components (flybacks on those are bitchin’) and part out some transformers from commercial microwaves; then just use some of the nossler ballistic tip bullets from the gun shed as ammo.

    Not even the trolls could say that wouldn’t be a hack.

  21. Chris says:

    Epic, really well made.

    One little comment, end of video the motto “Where Neccessity Meets Innovation” – Necessity, has one “c”

  22. zero says:

    and it starts with a 666 when powered up :))

  23. macona says:


    What’s the ESR on the caps. Most high farad caps have a high ESR that will limit the output current of the cap.


    Hockeypucks are the way to go. Just need to devise a clamping mechanism for them.

    Also I think fewer turns of heavier wire for the coil might be better. I wonder how long it is actually firing for.

  24. Bob says:

    need to test on bellistics gel.

  25. Xtremegamer says:

    now an automatic loading system and faster charge time :) probably a safe switch could be practical

  26. sd says:

    +1 internets for GLaDOS!

  27. Jess says:


  28. Tom says:

    A bit of MechWarrior music, too ;)

    Lovely build!!

  29. jeff-o says:

    This would be perfect with a mechanical injector; perhaps a pair of spinning wheels that inject the projectile into the coil, and a sensor that triggers the coil at just the right moment.

  30. Mike says:

    @macona the 350F has 2.5 mOhm and the 5000F has less than 0.25 mOhm. Yeah you don’t want to mess with the big ones. heh.

  31. BobSmith says:

    Torvaun: Have you ever fired a bullpup rifle? The magazine is in the same position as the capacitors (if I have it right; they’re the big blue things in the stock, right?). The magazine on a bullpup isn’t in the way of anything. This setup looks fine to me, and I love the look of the build. Could use it to infiltrate a scifi convention, dressed up like a generic space marine, and off a nerd you don’t like.

  32. KJ6EPL says:

    Has anyone ever tried a two-stage electro-mechanical gun? Like taking the spring action mechanism from an airsoft or bb gun and adding a coil to the barrel?

  33. Alex says:

    Would get a much more potent shot if the projectile was much smaller. So much energy is being expended to make a massive projectile travel relatively slowly. A projectile a third of the size as currently being used would make a dramatic improvement to velocity and impact force.

  34. BP says:

    Alex: I’m not very good with electromagnetism, but I suppose projectile has to be sufficiently large to be properly accelerated.

  35. mio says:

    Break skin? These things should be built as lethal as possible. Right form factor and you should have a billion dollar contract on you hands in no time.

  36. Nick says:

    You’ll never see me putting those caps under my armpit, I’ll tell you that!

  37. Nick says:

    If you put a piece of neodymium in that projectile from a dead hard drive the projectile would become leathal.

  38. Torvaun says:

    BobSmith: Are you suggesting we use the rear of the capacitor setup as a shoulder stock? It doesn’t really look like it’s got the stability/sturdiness for that.

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