Carrot's Bulpup Shotgun. This is my shotgun. It's bulpup as the name suggests and it shoots four bullets in one shot. The magazine is removable and nerf attachments can be put on the attachment rail at the top of the gun. Credit to MyOmy for the rail.
Step 1: Internals
The gun is really simply so I don't think it's worth posting full instructions
Step 2: The Magazine
Step 3: The Firing Pin
Step 4: The Side Panel
Now just pop that on the main gun, add elastics, place the rod in and final the loaded magazine. And you're done. Enjoy.