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No, this is not one of the sci-fi video game replica weapon props I keep posting about—it’s a real, functioning homemade coil-gun by Jason, aka YouTube user Larsplatoon, aka Photobucket and user Saz43, who has been working on it for two years. It’s billed as a “1.25kJ Coilgun,” but I dunno how that figure was computed. If it is muzzle energy then projectiles from this weapon deliver more kinetic energy than a .45 handgun but less than an M16 rifle, which I frankly doubt. But judge for yourself by clicking the embedded player below to be taken directly to the test firings at 2:50, in which various housewares get shattered and punched full of holes. I’m guessing 1.25 kJ is the theoretical maximum energy that can be delivered by the capacitor bank, and that the real muzzle energy is significantly lower.

Still, an extremely impressive project in terms of technical achievement , aesthetics, and “marketing.” It raises an interesting question about the point at which “backyard ballistics” type projects cross the line to violate the unwritten rule here at Make: Online about not covering weapons or defense-related projects. Don’t get me wrong, I think this is awesome, but if Larsplatoon and/or other amateur electromagnetic cannon experimenters get much better at what they’re doing I may have to start thinking twice about passing these along. Don’t try this at home, kiddies! [via Hacked Gadgets]


Sean Michael Ragan

Sean Michael Ragan

I am descended from 5,000 generations of tool-using primates. Also, I went to college and stuff. I am a long-time contributor to MAKE magazine and My work has also appeared in ReadyMade, c’t – Magazin für Computertechnik, and The Wall Street Journal.

  • RufusTheGreat

    It’s a nice bit of work. A perfect example of how to make things in stages. Excellent execution and nice scrounging. I’m impressed that the projectile doesn’t flip around while in flight. Good fundamental use of concepts that are all 2nd year EE stuff. Too bad it has the ability to do bodily harm or it would be a great demo or project in a classroom.

    Though it’s a little disconcerting that you plug the battery in while standing in front of the muzzle.

    Since the video says 1.25kJ of stored energy at 400V, I’d assume that’s just the E=0.5CV^2 worth of energy in the caps and not the muzzle velocity. If it discharges all the way to 0 volts then 1.25kJ has gone into the coil, but since it also says an estimated efficiency of 1-3%, I’d assume that only 37 J or so are turned into kinetic energy. That seems low, but my sanity check spidey-senses are failing me here, I usually don’t work in small values (I work on cars)… anyone else?

    • berettanut

      If we are working with a 500-600 grain projectile and 100-150 fps velocity, that gets us very close to the 37 J. The damage inflicted and penetration seems to be accurate for the 27 ish ft-lbs.

  • Lunas Eclipse

    i would need a range at which the projectiles could fly and i have doubts about flight stability