When I was building it I didn't know how well it would fire.
It has only one glitch:
the amo sometimes gets jamed and to fix the jam, you have to put your finger over the barel and blow to release them.
note: it won't fire with the barel plugged.
Step 1: Part one: the barrel, amo chamber, and amo
you'll need 25-26 of the amo(see the yellow box below).