A Homemade 12 Gauge Shotgun

This interesting homemade 12 gauge shotgun is of a straight blow-back design and very simple to construct.
The 12 gauge shell is simply inserted into the barrel, with the bolt in the cocked position. When the trigger is pulled the bolt flies forwards and the shell is fired. The trigger is perhaps of one piece with the sear built into it. The barrel looks like it is made from 1" pipe.