what you need:
-barrel material (1/2in petg pipe, 1/2 cpvc pipe, brass pipe, or hollowed out marker)
-some sort of glue (hot glue is reccomended)
-sand paper (optional)
Step 1: Unscrewing the gun.
get your screwdriver and unscrew the four screws on the side of the gun and open it up. the insides should look like this. (sorry about the red line, i had to get this picture off of nerfhaven.com) edit: pictures are from gengar003 on nerfhaven