@DanielOR: The Ideal Gas Law breaks down when intermolecular interactions increase, namely 1) under high pressure and 2) under low temperatures. For our purposes, the high temperature of the plasma effectively cancels out the high pressure. Besides, we only need to use the van der Waals corrections when we need to know exactly what the pressure [volume/moles/whatever] is. The general principles of the Ideal Gas Law still guide us.
@SirMoric: The ETC concept was invented well after WWII [and the flak 88]. While modern formulations of gunpowder do indeed burn more slowly than the old black powder, it still doesn't last long enough to maintain barrel pressure as the bullet moves towards the muzzle. However, there is the U.S. Army project using separate sections of gunpowder progressively ignited by electric charge.
@Darkpriest667: Chemical reactions do not and can not create radiation, or indeed any changes in the nucleus. Sorry, but you must have mis-heard whatever it was you overheard. You could, of course, suffer from burns due to the plasma... And no, it doesn't need to be hot enough for fusion. It just needs to maintain enough pressure to keep the bullet accelerating the whole time it is traveling down the barrel. If you could master enough energy to get fusion, you wouldn't need the bullet anymore.
