This is why I wonder what all the freakout is with 3D printed guns which could take a week or more to make. Here…a trip to Home Depot and an hour you are good to go. Oh keep in mind this is a cap gun, but you could apply this (metal pipe thought) to make it real
http://www.instructables.com/id/Awsome-Mouse-Trap-Powered-Riffle-That-Shoots-and-I/?ALLSTEPS