Only one problem. It needs 6 brand new D batteries to get anywhere close to the claimed 3 shots/sec. Those aren't cheap, and need to be recycled.
Fortunaately, there's an easy fix. 6 x 1.5V batteries is not too far off from a 9.6V rechargeable racing pack.
Parts:
- 9.6V racing pack. You can get a decent one with a charger for $15. Try to get a charger which shuts off automatically when the battery's charged; the cheap ones don't, which will fry your battery if you forget and leave it plugged in too long.
- Extra connector for racing pack. I chopped mine off one of those cheap chargers, which came with a remote control missile launching tank.
- Alligator clips.
- Wire cutters
- Soldering iron
One end of the battery box has metal pads on it. If you hold the box so those are on the left, that matches my picture. Clip the - (black) wire from the battery pack onto the spring closest to you. Clip the + (red) wire from the battery pack down into the far right connector. It should look like this:
Now, put the rechargeable battery in the battery box and slide it all into your Nerf Vulcan gun. Add darts, and fire away! It doesn't fire any farther (since that's dependent on the spring action in the gun), but it will fire a lot faster. You should get about 3.5 shots/sec on a fresh charge. And you can always switch back to those D batteries in a pinch.
Disclamer: Use this mod at your own risk. I'm sure this voids the warranty. While I haven't seen the slight over-voltage burn out the motor of my Vulcan or break the internal action yet, that doesn't mean it won't happen eventually. This mod is not endorsed by Hasbro.