A Homemade 1.25kJ Coilgun

Steve Johnson
by Steve Johnson

This homemade coilgun is very impressive.

There has been a debate on AR15.com about how powerful this gun is. My guess would be a 800 grain slug traveling at 100 ft/second and generating just under 18 ft/lbs (24 joules) of muzzle energy. This is guesstimate fits in with the inventor’s estimate of 1-3% efficiency (1250kj * 0.03 = 37.5 joules).

This gun would still have recoil. Newton’s third law of motion cannot be circumvented by the use of magnets. Please correct me if I am wrong (UPDATE: I am!), but I think the recoil would be spread out during the time the projectile passes through the “barrel” (magnetic coils), unlike a firearm where the recoil occurs after the bullet exits the barrel. A marksman would need to counteract the recoil whilst aiming the gun, much like a machine gunner. This would have a horrible effect on accuracy, but the felt recoil would probably be more comfortable.

[ Many thanks to Ben and jdun1911 for emailing me the link. ]

Steve Johnson
Steve Johnson

I founded TFB in 2007 and over 10 years worked tirelessly, with the help of my team, to build it up into the largest gun blog online. I retired as Editor in Chief in 2017. During my decade at TFB I was fortunate to work with the most amazing talented writers and genuinely good people!

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  • Kelli Kelli on Mar 29, 2011

    Hey I was wondering how much this gun weighs.


  • Ledernes fagforening Ledernes fagforening on Dec 17, 2012

    magnificent issues altogether, you just gained a logo new reader. What would you recommend in regards to your post that you just made a few days ago? Any sure?