"A railgun is a device that uses electromagnetic force to launch high velocity projectiles, by means of a sliding armature that is accelerated along a pair of conductive rails. It is typically constructed as a weapon, and the projectile normally does not contain explosives, relying on the projectile's high speed to inflict damage. The railgun uses a pair of parallel conductors, or rails, along which a sliding armature is accelerated by the electromagnetic effects of a current that flows down one rail, into the armature and then back along the other rail. It is based on principles similar to those of the homopolar motor." SF
Now this has little to do with Mu Gu Gai Pan.
I have long been interested in these gadgets. I remember a NOVA feature that looked at what they called "mass drivers." This is the same thing I suppose. The device was also featured in Heinlein's novel "The Moon is a Harsh Mistress" in which big ones were used to fire loads of rare earths and the like at target ocean areas on the earth for retrieval. How well that would work is beyond my ability to judge.
These things typically will fire metal bolts at hyper-velocities at maritime targets. Cool. pl