I will show you how to make a semi-auto relvolver riffle out of K'Nex. You can make as many barrels as you want. These are the magazines. You can also put as many rubber bands as you want but don't put too much so that you can't pull the firering pin. Simply look at the pictures for instructions. It fires white (black for me)rods. In this instructable, you will need to sacrifice a lot of pieces. Two gray connector, one gray rod, a yellow connector(me it's gold)and four blue connector. This gun is VERY pricise and shoots VERY far compared to the average K'Nex guns.
Here's a video in which i use my gun. The purpose of the video wasn't on the gun so don't complain and im speaking french in it. Go to 2:15 minutes to see the gun in action. Little different version but same concept.Link to this video on youtube