Actually the barrel is inside the blade, you basically use it like a normal sword but shooting it on impact creates a vibration as well as firing and well... It kinda hurts
Well, it is final fantasy, don't expect it to be realistic
PS: I believe it must be the coolest weapon ever imaginated.
Well, I guess the less you expect it, the more awesome it is
That's why before a game comes out, the devs don't usually show the whole progress, or else it would be rather disappointing once the game is out