It involves a 555 IC timer circuit to trigger the sound and LED effects, and a 4017 decade counter chip to make the LED chaser effect seen at the rear of the gun. The circuitry is pretty basic and was my first real scratch-built electronic project. The blaster build consists of 2 sub-projects : building the electronic effects, and making the gun itself.
I modeled mine after a Hero (that means it was used for close-ups) ROTJ Blaster prop that recently sold on ebay. The project was more about learning electronics than anything else, but in addition to the new understanding of how to build blinky lights, I ended up with a pretty neat toy. I wanted one that really 'worked' and looked good, so I made my own. Neither of them shoot bolts of red light accross the room. There is a blue plastic dart gun by Hasbro, or a great looking, solid but non-functional $400 model from Master Replicas. If you fancy a Star Wars rebel trooper blaster pistol, you have basically 2 commercial options.