This is how i built my Boba Fett Starwars Blaster for my Halloween costume. I wish i had better documented building process but, it was not to hard.
Step 1: The Blaster
I used a Rebel Alliance Nerf Blaster i bought at wal-mart for $20 bucks. It was blue and orange. I took out all the screws holding it together and tore out all the guts and the barrel. Then I drilled holes just large enough for led lites to be passed through the holes. The leds came from a necklace a found at the local party supply store for $3. Note: the pet laser attached to the blaster.
Step 2: Making the stock
The stock is made from wood. I found a section of 3/4 inch dowel left over from another project for the stock and a scrap piece of 2x4 is the butt plate cut to shape using a skilsaw. Bored out a hole in the 2x4 butt plate with a drill for the dowel to be inserted and held in place with hot glue. The dowel then goes into the back plate of the blaster. I had to bore a hole here also using a cone shape metal grinder used in metalworking made just for drills. You can find them at lowes hardware. The dowel is then hot glued in place and i also tapped a screw through the blaster into the dowel inside...
Step 3: Attaching your hardware
Now is the time to paint your blaster. I highly suggest you paint the blaster before you insert and hot glue the led lights. you can go back with a artist brush and touchup areas later.
Step 4: Attaching the sling
I used a ak-47 sling for the blaster. The attachment bars are picture frame mounting hardware left over from building the knee armor. I used a drill to bore out a hole in the plastic blaster then tapped in screws and attached the sling.