This is the "Manning's Pipe-Gun MK2" the newest model of the world's first 3d printable Shotgun, following in the footsteps of The Liberator made by Defense Distributed.
This Design is based on the Filipino Guerrilla Gun/Four-Winds Shotgun, boasting a slap-fire mechanism for a 12 guage buckshot round. Simply get Shapeways to print your mk 2, and reload like you would a four-winds shotgun.
Once again, this is merely a proof of Concept. I am not ballsy enough to test it myself, but by my calculations I'd expect that only the stainless steel would handle IRL use. I am working on a MK 3, adding a safety lock for transport. The design should still look pretty as a cosplay "cyberpunk" gun.