Quote Originally Posted by DarkElfDude View Post
-plasma, now here is where it gets more complicated, a plasma rifle would take a way to keep the plasma in a more dense form since plasma is more of a superheated gas it would most likely just dissipate and melt the barrel (and maybe the user)
Strictly speaking, plasma just needs to be ionized gas--something that can be done at more lower temperatures by applying electrical power. Any decent university (or for that matter, a lot of bars and diners) will routinely work with plasma. With enough applied electric field, you can etch through materials without getting too hot (and by "too hot" I mean melting the metal or glass used to contain the plasma.)

The big limitation I see is the distance. Even within a low pressure chamber the size of a microwave, mean free path becomes a big issue has your ions lose energy to collisions with gas molecules. If you jack up the power (which you would probably have to in order to cause damage fast enough to be tactically useful) you would have a lot more momentum to start with, meaning you could afford to lose more before becoming useless. Still, you would lose a huge fraction of your power over just a hundred feet or so. Worse, this energy doesn't just disappear--most of it will go into random collisions with air molecules closest to your gun. Right now, this would just mean that the plasma dissipates and starts heating up the air closest to your friendlies. However, if you're coming up with a way to make sure that your plasma can traverse a useful distance, I have no clue how this would work. It could potentially end up like firing a giant shotgun full of superballs through a thick forest--most of the balls will keep going in the general direction of "away from shooter," but a few will hit something and bounce off in a different direction. Even if the proportion of plasma ions that bounce back is small, remember that the shooter will be exposed to loose plasma for every shot fired.