). You must have both accuracy and precision to make for a useful weapon when there is only one weapon firing. If you can live with low precision, then you have to mass fire from multiple weapons. If you can live with low accuracy then you have to repeat fire over an extended period of time.
A flame is not solid, not liquid, not gasseous, and not energy, therefore it must be plasma.
A flame is, in fact, a gas. It's just a very hot gas, hot enough for the electrons in the various atoms/molecules of the gas to jump to higher energy states, and then emit that energy as light as they fall back down to their groud state.
So a rifle with its sight misaligned might be inaccurate but precise, while a shotgun shooting pellets might be accurate but imprecise. Is that the basic idea?
Regarding flame, I have seen it in scientific literature described as plasma. It could very well depend on how hot a flame is in question. It might also be a blend of gas and plasma. Really, though, the point is moot since he isn;t talking about flame throwers in the first place.
There is no such thing as "precise but inaccurate" with weapons fire. That is something that engineers and experimental scientists talk about all the time, but it doesn't apply to soldiers (unless they're from Kentucky ).
As for a weapon that uses ionized plasma, you would need very high velocity (basically approaching being a particle weapon) or a balance of positive and negative ions (a more usual solution) to maintain stream coherency over longer ranges. Generating an extended magnetic field wouldn't be very effective unless you were able to extend the field almost all the way to the target...in which case, it might make a better direct weapon itself.
Flame itself is a form of plasma because the actual flame consists of matter that is not bound into molecules, as it is in the process of being broken free from one molecular configuration and falling towards a different energy solution and molecular configuration. It is true that, by mass, most of the matter in the general vicinity of a flame is ordinary hot gas. But the flame itself is definitely a plasma.
As for constructing the ranged plasma weapon, the only reason the plasma isn't going to blow up in your face in the first place is probably because the weapon has it contained in essentially donut shape with a magnetic field. The moment the plasma actually leaves your gun, though, or rather, once it is no longer contained and has something, anything, to react with, the result will be a rapid and violent expansion of the energy stored in the plasma. ie. BOOM!
Short of just creating a fictional part to the gun that somehow keeps the plasma focused / non-interacting for a number of seconds after leaving the gun, I can't think of any way a projectile plasma weapon would be plausible/practical. Maybe that's why it's science fiction? =Þ
This site I found by googling "plasma weapon" seems fairly well thought out and helpful:
http://www.stardestroyer.net/Empire/Essays/PlasmaWeapons.html
One must presume that the effect is achieved by some type of primitive "cohered plasma" technology. The simplest such effect is to combine both positive and negative ions in a weapon's discharge to prevent it from simply exploding on leaving the weapon (used with high-velocity, unguided plasma weapons). Given the need of a low velocity plama bolt for some form of propulsion anyway, it would seem logical to give it a very simple seeking capability.
As to how this would be accomplished, it is clearly beyond human technology, and even describing it in detail would strain existing scientific concepts. So I'd just put it in the realm of "handwavium" and leave it there for the time being. It's on the same level as trying to discuss traveling to the moon with a medival Bishop working under Aristotle's model of the universe.