The SPAS 12 is a 12 gauge semi/pump action assault shotgun. What makes the spas 12 cool is how you can switch it between gas operated for conventional rounds to pump action for lighter gas or beanbag shells. it took me about two hours to make pretty easy it took me two hours because I was cycling through cleaning the bathroom watching the Alaska Experiment (love that show wish I could go but I'm still a minor) and building this.
I love the design and everything, but there's one little detail that I must catch you on. SPAS stands for Sporting Purpose Automatic Shotgun. Back when it was made, the US disallowed it's import due to it being a combat shotgun. The name was given in a (failed) attempt to circumvent this. I think that the ban has been lifted, but I'm not sure.
Quoting Chris Kweon
wait does that really shoots???
it doesn't shoot any bricks or rubber bands if thats what you mean, but if your asking if it would actually shoot shot shells well, I might be able to make a working mechanism but I doubt the plastic pricks could hold the pressure from the released gases, it would probably just explode the bricks would melt and there would be molten legos all over me and it would burn me and I would die, I hope that answers your question :)