A full-auto Gauss gun probably won’t hurt much

While it may only be able to shoot a few cans right now, we certainly wouldn’t want to be in front of [Jason]’s fully automatic Gauss gun capable of firing 15 steel bolts from its magazine in less than two seconds.

The bolts are fired from the gun with a linear motor. [Jason] is using eight coils along the length of his barrel, each one controlled by an IGBT. These are powered by two 22 Volt 3600mAh LiPo battery packs.

As for the mechanical portion of the build, the bolts fired from this gun are actually 6.5mm nails, cut off and sharpened. These are chambered from a spring-loaded magazine, with each new bolt put into the breech with a small solenoid retracting for an instant. The frame is constructed from a square aluminum tube with additional pieces cut with a hacksaw and bent with an impromptu bench vise brake. If ever there was a person deserving of a bench top shear/brake, [Jason] is the man.

The muzzle velocity of these bolts is about 40 m/s, with a muzzle energy that’s about 3% of a .22 LR round. Not deadly, but more than enough for picking off a few cans and bottles in a garage. You can see the video of this futuristic Gauss machine gun below.

97 thoughts on “A full-auto Gauss gun probably won’t hurt much

  1. Beefore my rant: This gun is fucking awesome.

    Wouldn’t it be more effective to just use all that electromagnetic energy to hit the nail with a single solenoid? I could be wrong, just wondering if anyone has tried it. Also has anyone tried magnetizing a nail for extra kick?

    1. With a single solenoid, you have the problem of magnetic saturation. Like putting water into a sponge, you can only apply so much magnetic force to a piece of iron eytc before it won’t much more effect.
      Using multiple coils means you can get around the saturation of the iron, and still get the velocity by adding energy in stages.

  2. I like this for two reasons.

    1) It has successfully incorporated design cues from the M41-A pulse rifle into an abstracted monolithic interpretation.

    2) It is an operational coil gun. Pew pew!

    One day I expect technology of this kind will be used to accelerate spent nuclear fuel to escape velocity inside a toroidal race chamber at which point it will be released to hurtle towards the centre of the Sun. Clean energy for everybody!

        1. ahh but what we call “spent” fuel is actually still useable in certain reactor types. Using the “spent” fuel in those reactor types actually results in byproducts which have much less lengthy half-lives and is far easier to deal with.

          1. By your own definition couldn’t it be said that what was meant by “Spent” was that it had already been run thru every process we know of and all we’re left with is useless green schmutz that even frightens cockroaches?

        2. “Spent” means that it only has 98 or 99% of it’s energy remaining. Better designed homogeneous reactors could extract FAR more energy from this fuel than the stupid kettles we are currently using for power.

          1. I see a time were we dig up old nuclear waste again to reuse it with better reactors.. Maybe there would even be wars about what nobody ever wants right now!

      1. or put small vanes (like an arrow) or rifled impressions on the bullet itself so once it encounters some air resistance it imparts its own spin. like a stabalizing sabot, or shotgun slugs. the 12 ga slugs i have for my shotgun have angled depressions at the rear and of the slug so once it gets out into the air it starts spin-stabalizing on its own. The smooth bore of almost all shotguns don’t impart any spinning, as rifling them would cause issues when you switched over to buckshot or smaller with the balls hitting the lands and possibly riccochetting in the barrel. not fun for the shooter….

          1. At some point, I need to see if there is a way to induce the right magnetic eddies to cause the projectile to spin. I’m pretty sure the direction of current flow to set up the right field would need to be in the direction of projectile travel. Maybe the design could have some carbon rings at intervals in the barrel and the projectile would complete a circuit between them.
            The slug would need to be better engineered for magnetic and electrical properties though.

        1. The problem with your idea is “air resistance”. If you add stabilizing fins, it’s better they work like on a dart instead of making the projectile spin because of the added drag. Spinning is better because it makes imperfect bullets fly straight, but since the muzzle energy is just 10 Joules, any air drag will kill the range.

          It’s possible to make magnetic rifling by having a slight oblong cross-section for the magnetic coils and similiarily the bullet. To make it round again, you pad it with a non-magnetic material. That way, it will try to twist to align with the densest field, and rotating the successive coils in a spiral will likewise make the bullet follow a spiral.

      1. Would it be possible to form a monopolar motor at the first coil to induce rotation into the round before firing to achieve the same effect as rifling?
        Magnets, how do they work?

        1. Good idea, might be easier with a ball bearing and a wheel with a DC motor to spin the projectile up… would be bulky. Monopoles don’t exist, at least not in our real world without crazy science and machinery.

    1. I would like to investigate the possibility of using magnetism to spin the projectile in the chamber first. Then once it’s fired (as long as it’s kept from hitting the sides of the barrel) it will continue to spin. You would lose all the drag that a rifled barrel causes and still have a lot of rotational velocity.

  3. Wow this is an incredible project with an incredible writeup! Makes me want to build another coil gun. Now, a few thoughts.

    First, I don’t think he really needs those massive IGBTs for switching. He’s using them as low duty cycle switches to simply connect a 50v battery to his coils. Yeah there’s a lot of current, but small TO-220 or TO-247 package IGBT’s with a reasonable current rating would probably be fine. I highly doubt he’s getting anywhere near 300A through those coils at 50v with this setup…as that would be ~15k watts. This would be something to test though.

    I probably would have went with a higher voltage by charging capacitors like he initially planned. You’re never gonna get the surge from a battery that you can with a capacitor. He could’ve used cheaper SCRs by doing this as well. The reason behind using caps and higher voltage is that it allows way more current in the coil… and as he said, “Force on the projectile is proportional to coil current multiplied by turns of wire”. Furthermore, higher voltage allows thinner wire to be used.. which allows more turns! The boost converter can always be made smaller! That’s no excuse when you’re a hacker! :) Or simply add more batteries in series to charge higher voltage caps.

    Finally, he probably doesn’t need that many diodes in parallel for the coil anti-parallel diodes. Again, experiment with this. you’ll know when they are too small :) The resistor across them is very smart though.

    Just food for thought. Again, great project!

    1. “Force on the projectile is proportional to coil current multiplied by turns of wire”. ”

      At least until the material of the projectile starts to saturate. That rule applies with low field densities only, which has always been a problem with coilguns. That’s also apparent in the low efficiency figures of just 7%.

      To achieve higher forces and ultimately higher velocities and energies, you need a gun that works on the induction principle, similiar to a Thomson’s coil.

          1. The ones I was talking about are specifically Linear Induction Motor
            (LIM) or Linear Syncronous Motor (LSM) as on paragraph 3. Rail guns
            linked in paragraph 2 has the nasty habbits of destroying their rails.

            >They are usually of the AC linear induction motor (LIM) design with an
            active three-phase winding on one side of the air-gap and a passive
            conductor plate on the other side.

            >The low-acceleration, high speed and high power motors are usually of
            the linear synchronous motor (LSM) design, with an active winding on one
            side of the air-gap and an array of alternate-pole magnets on the other
            side. These magnets can be permanent magnets or energized magnets.

    2. Oh, and the more turns of wire you have in a coil, the higher it’s impendance, and the slower it reacts to a voltage pulse. That’s a problem because it needs to turn on and off at the correct time as the projectile enters and exists the coil. You can force it to react by using extremely high voltages, but generating and switching them is problematic, and you’re still running the projectile in the saturation region where more magnetic field yields progressively lesser and lesser increase in force.

      1. Interesting. I didn’t know that, but it makes sense when I think about it. Many of my points still stand – he could still get away with smaller and cheaper switching electronics in his current design.

        Also, I guess the low impedance of his coils is how he gets away with so many so close to eachother. His coils, based on your thought, should react to voltage very quickly. I postulate that this allows very little needed distance between each consecutive coil.

        I guess that’s why the big boys (Gov’t) isn’t really interested in coil guns… they reach saturation before enough energy can be exerted. Then you need a railgun or other induction based device for real power.

        Is there any limit or “saturation point” for induction based devices? or is it simply a factor of them melting from too much power?

  4. I think he needs a denser magnetic field with a higher flux. A non-conductive barrel surrounded by multiple coils, possibly in a hexagonal pattern, with appropriate phasing and alignment would greatly benefit his design… and it appears he has room for that in the build…

  5. the brivk IGBTs are a bit overkill … but THAT WOULD HURT LIKE A BITCH … may not be fast but it has allota force and seeing how much paintballs hurt and that you cant do THAT to a laptop or cans with one of those … and these are pointy!

  6. Also at least juding by the video (I admit to not reading his documentation) it seems he is only really using half the coil action. Only pulling the slug from coil to coil.
    I am sure the timing is super challenging, and the electronics more complicated, but could get considerably more power by reversing the field and pushing the slug out of the previous coil while puling into the second coil.
    Perhaps the time suck when the field collapses in order to reverse polarity is too great?

    1. 2 things on that..
      1- The nail isn’t magnetized. Sure it has a temporary field in it from being pulled, but I’m not sure that a reverse field behind it would have the desired effect. It’s mostly just a lump of ferrous metal.
      2- I would suspect that the time it takes the coil to build up a strong field in the first place is hindering his muzzle velocity. While the turn-on and turn-off of these can be dialed in for max speed, the time it would take for the field to break down and build in reverse direction could easily be high enough that the nail is long-gone. Maybe the first coil or two things are still slow enough. Ideally each progressive coil should have decreasing inductance for faster field buildup. This comes at the expense of using more current for the same flux strength. ahhh damn now I want to build one.

  7. That needs a 100 round magazine drum ASAP. He needs to triple the energy dumped and increase rate of fire to “oh dear jesus” levels. AS in 300 rounds per mini levels.

    Makes me want to buy a buttload of transformer wire and start making things that will get the house raided by the ATF…

  8. non electronic engineer here but instead of beading off the energy from the last coil could that not be dumped into the next coil or used in some other way to increase performance / efficiency?

    ow and congratulations on a very impressive piece of hardware man.

    1. Reading along and I was also wondering about possibly “harvesting” that collapsing field.
      Once coil “A” is pulsed it gets re-routed
      ( via software and silicon )
      to catch the collapsing field of coil “B”.
      But then I wondered if that would create such
      a parasitic load on the coil that’s driving the slug
      that it wouldn’t be feasible.
      I imagine if it could be done (on “paper” )
      the parts count and added bulk,
      timing of the switching components,
      then cooling all of it ….etc
      would be practical outside of a test lab.

    1. yeah, the R/C community (airplanes or cars) have some pretty amazing technology.
      My scooter build(using pretty much all parts for r/c models), for instance, can output in the upwards of 3600 watts continuously.

  9. Thanks for the comments, lots of good ideas too. Best idea so far: Triple energy/drum magazine/300rpm. If I build another one, that’s what I’ll go for, possibly in conjunction with fin-stabalized projectiles, better designed coils, and maybe LN2 cooling.

  10. The use of high c rating iIPo batteries is interesting, but combined with a medium sized capacitor (for each coil) i think it would be even more powerful.
    Also ofcourse a railgun version of this would be amazing.

  11. Well, that’s certainly interesting and very different from his other coil gun (which has been featured on here previously) which used one coil but a big cap bank to charge up and then dump lots of amps through an SCR.

    I wonder if his next one will be meeting in the middle with a couple of coils and some sort of short charge/medium storage of energy.

  12. I think the comparison to a .22 is false. Would you chose to be hit in the chest by a 1000ft/sec .22, or a 50 ft/sec spear? The mass matters, and those bolts weigh a whole lot more than a .22 lr bullet.

    1. keep in mind though – they’re talking about muzzle energy, not so much velocity. a spear weighs a lot more so it has kinetic force applied with a higher mass behind it. it’s also not a fair comparison because a bullet actually operates on blunt force and hydrokinetic shock (eg hydrashok) to do its damage. a better comparison would be a war hammer vs a bullet, but then you’re only allowed to deal with the primary point of impact for sake of energy delivery argument

  13. Those coils look pretty hefty, I’m guessing the limiting factor on the power is the battery and associated circuitry. Hook that thing up to a MOT and see how far it’ll shoot.

  14. Muzzle velocity does not equate to energy. Best to consult someone who knows some ballistics before making such statements.

    Considering the weight of the projectiles and that one punched through the laptop screen, I’d say you’re looking at between 20-50 foot lbs of energy, or about 1/3 that of a 22. Just not the kind of velocity a 22 gets. But you have to realize that the projectile that is firing is MUCH bigger than the little 22 bullets. It wouldn’t be lethal, that’s for sure, but I wouldn’t want to be picking one out of my skin, or from an eye socket. Remember, paintballs aren’t that fast or heavy either, but they have a good cross section.

  15. Loved the video. Just wanted to throw in a quick question. The first thought that came to mind watching the video was “large needler”. I’m sure at least a few people looking at this must be familier with sci-fi needle guns. Would making the ammo smaller and modifying the coils/”barrel” have detrimental effect?

  16. What is the fascination with rifling? Judging by the rate of fire / power / size of projectile, it would be an ideal close combat weapon, which requires little accuracy. Perhaps if you had the new free energy tech to add a’lot more power into a new design for longer ranges it would be practical… But in its current state, don’t you think other factors about the weapon are more pressing? While the chance of Bloom Box tech incorporated to a civilian made weapon are unlikely ( Because well… uncle Sam makes sure his tech lvl is higher than the people can ever have ) you can still tamper with the projectiles themselves to increase accuracy. There’s just too many factors for barrel rifling to be effective in a Gauss / Coilgun… Factors that can be researched.

    1. I’m an idiot but how would steel balls fare in a coil gun? that will solve the problem of making the projectile spin and will make a damn good close quarters weapon if it can be delivered in a high ROF

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