“The “CG-42″ Gauss Machine Gun is an eight-stage, full-auto coilgun.

“A coilgun is a linear motor. Electronics hobbyist James Paul has developed a great mathematical model of a basic linear motor on his website Coilgun Systems. Please read about his model here. A key conclusion drawn from the model is that coils become more efficient as projectile speed increases. This conclusion rules out a single-stage coilgun as a good design because full power is dumped up front when the projectile is still moving slowly. A much better design uses multiple, lower power coils to distribute the acceleration over a longer distance so less energy is wasted during the initial slower portion of the acceleration. As the projectile speeds up, subsequent coils become increasingly efficient so adding more coils and lengthening the gun improves efficiency and increases muzzle energy. That means an efficient, powerful coilgun will be long and have as many stages as possible.

“Also, large currents are not needed to produce this more gradual acceleration. This is good for a full-auto coilgun, because it eliminates the need for capacitors, charging circuitry, and their slow recharge times and power losses. There is a lot more to understand about coilgun physics, but this bit of knowledge can already seriously improve the design.”

So this is a thing now. Too bad it wasn’t 3D printed, otherwise the project might get a lot more press.

Anyway, it’s imperative that you check this out: Delta-V Engineering.