Electro-Muscular Disruption Device So here is how it is. In Transcendence, a Science Fiction novel that I am working on, I have this device that I could use some help in explaining how it functions. It is an EMD, an electrical weapon that disrupts muscle movement with an electric shock. This device is shaped like a small egg on its side and is mounted on the side of the barrel of a T-1 Assault Weapon (the T-1a most notably) and sighted in to use the weapon's standard IBIS sight(basically a reflex sight). Here is the trick though, I need this device to be able to fire an electric charge without the use of wires or any other assistance at short to moderate ranges. I am wondering if you guys have any ideas as to how this could be accomplished (I am open to replacing the electricity with something else if it is easier to explain that way). Thanks ahead of time. I will continue my research into this subject on my own as well, but any information or advice you could offer on this front would be greatly appreciated. Also note that the device needs to be compact, which means it can’t use an extremely huge amount of power (at least not any more than a nuclear battery could provide), and should be able to be fired repeatedly.
Unless your civilization has developed energy weapons, you will probably have to deliver the electrical charge via a solid round. So maybe the gun shoots out an electrically dart? Shooting out a stream of electricity would be dangerous because electricity tends to follow the path of least resistance. So anything that would attract it such as wire or any conductive metal might pull it away from the intended target.
You'd have to have something for the electricity to travel along. That is, unless you plan to rub the bad guys with lots of balloons for a long time. Other wise you'd be just as likely to zap yourself. Of course, while this wouldn't work so good for a gun, you could have them function like grenades by having them just emit an electric field that could screw with peoples nervous systems.
Perhaps you could do some research into how lightning works, as it is an electric charge over distance (ground-to-cloud, etc.) and incorporate that into the device. Sci-Fi doesn't require you to explain something in such detail that a scientist could go in and create the device, but just enough that people will buy it. Star Trek describes warp travel as faster than the speed of light but, as of our current technology, is impossible due to the theory of relativity.
Having this device mounted on a rifle will give you no end of problems explaining how it works. You might be better of making it it's own weapon. For ideas of how something like you discribed might work, look at how an electric eel attacks it prey. An electric eel has organs that creates and release the charge through it's cells. Each cell can hold a small charge but as it fires the 'pulse', each cell adds it's charge to the next in sequence until at the end when the charge can be over 650v when fired. If you use (or butcher) that logic, you may be able to come up with a type of sonic pulse thats electrified. Don't quote me on this but it think this was how the tesla cannon was supposed to work.
There actually already is a similar device, though right now I can't find a source. What it does (IIRC) and what yours could do, is send forth two streams of charged particles (ions or electrons, doesn't matter which). These streams would "end" on the muscle you want immobilized. In passing through air (this only works in air, or some other dense atmosphere) they ionize the air molecules and create an electrical circuit, going from the weapon via the first stream to the muscle, through the muscle to the other stream, and back to the weapon. You can then send your electrical pulses along this path. Begging your pardon, but this wouldn't work too well. A person hit by an electrically charged ball would feel a small spark when it touches him, and that would be it, then the charge has spread out over his body into a new equilibrium situation. Difficult to trigger a muscle with this, unless you discharge lots and lots of electrically charged balls at the right intervals. This is basically the same principle as what I outlined above. The visual effect of lightning is basically recombination of ionized air molecules with their electrons. The device I outlined above would look a lot like lightning when used, though the charge transferred is obviously much less. This would also work. You could have a cartridge with wires and electrodes that you have to "load" into your weapon before use.
I like your idea about ionizing the air, but I think that it would be far simpler to just go with the cartridge. On that note I could just drop the device entirely and have the cartridge fired from the 20mm grenade launcher.
I guess I should have worded that better. I didn't mean an actual electrically charged metal slug. I remember watching a tv show years ago where the MC had ammo that fired out charged rounds. Now that I think about it, they were more like darts. The bullets would hit the target, then a needle would stab out of the tip and the mechanism inside would shoot out an electrical charge. The target's entire body would completely lock up for something like six hours. That's probably a bit more sci-fi than what the OP wants though.
You want a 'taser' that works on a distance. There are also guns that shoot wires to deliver the shock (don't know their name). For inspiration, you may also look into a phenomenon called "electro-statical discharge" (that's the effect where an electrical charge is released from your finger if it comes close to a metal surface under certain conditions (cold weather)). Your 'egg' could be a capacitor. Air is a bad electricity conductor (=good insulator). Either fantasize a novel transport manner (maybe(?) some nanoparticles that create the transport function) or invent another type of charge (similar as electricity, yet chemically-based).
What you're talking about is an electrolaser. These are theoretical things, but the basics of it are so: You fire a high-powered laser that is susceptible to 'blooming', meaning it ionises air around it into a plasma. The colour of the laser is irrelevant. Shortly after, you generate an extremely high voltage. The current then takes the path of least resistance, which is the plasma path the laser created. The current then passes through the body of the target who twitches horribly from electric shock. There are some issues with using it in real life, but it's science fiction so you can handwave those mostly. Note that this would not be stealthy - firing it would create a high-pitched crack and a bright purple bolt of what is essentially lightning, caused by the recombination of the plasma into gas as Porcupine said. Make whatever modifications you need to get it how you want though, since the word 'fiction' is in the genre for a reason.