It also draws on the power of the user, hence the reason why Killy is suited to using it, because of this the GBE never'runs out' of bullets and has unlimited ammo so long as the user has power.
It also draws on the power of the user, hence the reason why Killy is suited to using it, and he makes a point of being the only person to fire it (by not allowing others to use it). It never'runs out' of bullets therefore, and has unlimited ammo so long as the user has power.