My first whack at it used an old drum bass pedal as a pivot and some small servos I had lying around, hooked onto an old airsoft pistol. At some point I might switch to a super soaker, but for now I kind of like the airsoft gun. It's all hooked up to the receiver on one of my crashed model airplanes, since I'm really just working some of the kinks out of the mechanical parts. Anyway, this is what I have so far:
And here's a video of the tilt and fire mechanisms in operation:
As you can see, the fire servo is a bit weak, wobbly, and susceptible to vibration, which makes it bump-fire in roughly 3 round bursts. I ordered a few larger servos for the next iteration, so hopefully I can take care of that issue.
Anyway, watch this space for progress...