Here's a video of my brother and me using our homemade rifles.
For the barrel of the rifle, I folded some cardboard. For the gunstock of the rifle, I folded a piece of cardboard in two and cut it such that it resembled a gunstock of a real rifle. For the bolt, I cut an egg carton and glued one piece to a broken chopstick then I glued it to another broken chopstick at a ninety degrees angle.