This is a video of Nerf gun lover Out Of Darts (he REALLY loves Nerf guns, and it shows) debuting his custom Zeus ball-shooting rifle, which he modified to hold 108 balls instead of the standard twelve. He uses a blower mounted on the back of the rifle to keep the balls moving towards the launching mechanism for full-auto blasting. There's also a video of the backpack mod he made which can hold up to 270 balls. That is a lot of balls. For reference, I have two balls, and one of them hurts right now because my pants are too tight and I moved my leg.
Keep going for three videos, one of this mod, one of his 3-ball burst fire mod, and one of the backpack.
Thanks to RobbyRob, whose Nerf gun broke mid-battle and started shooting the balls out of his mouth.