I know there is already a thread on this but didn't want to thread jack. I've come up with an idea on how to make one, but I wanted to get some opinions first. Basically, it will work like a spring gun. The bow string is like the spring. I have an old shotgun inner barrel I'm going to use with an outer barrel of some kind. I'm thinking PVC pipe or just a shotgun outer barrel. When I pull the string on the bow, it pulls back a piston and compresses air in a cylinder like a syringe. I need to decide if I'm going to use a hopper and how, if I need to, use elastic bands to pull the piston back to the first position. I want to know if anyone else thinks it will work. Here's a diagram. Ignore the hopper thing.