Lego guns

For the past few days I've been trying to build a Lego gun. All of my attempts were unsuccessful. Including this one. I've been looking on youtube.com for ideas to build one but the ones that they put on there usually only shoot a few feet. This one is an electric one because I don't like those ones that you have to cock back every time you want to shoot. The yellow/ grey thing in the back is the source of it. It's supposed to be used for making and programing robots but you can still use it for things like this. I programmed it so that when the touch sensor at the bottom is touched that the electric motor that the wire is attached to will spin. Since the motor spins way to fast and isn't very powerful I attached a worm gear (a gear shaped like a spiral meant for making gears have a stronger force but also a lot slower.) to the motor which turns that big gear. And the big gear drives another big gear below it which holds rubber bands between the notches. When each rubber band comes past the top of the gear it is supposed to fling forward. But instead all the rubber bands fling forward at the same time. I haven't figured out why so I'm going to make the same gun but the gear is going to be driven from the side and not by another gear.