Open Source Disc Shooter (Q48744)

This is a redesign of my prior attempt at building an open source disc shooter. I'm not sure which kind of disc would be best. So, I've designed 9 different kinds. There are three with 2 holes, three with 3 holes, and three with 4 holes (plus a center hole for each). There are three with those holes beveled up to the right, three not beveled at all, and three beveled up to the left. The barrel is in two halves, which should hopefully fit together. There's a firing pin as well, with notches for a rubber band. The cap is designed to be used with either one long rubber band or two smaller ones. I've included a sketch with some basic design elements. Eventually, I'd like to add a way to pop in a set of discs. Having printed and assembled, I offer the following notes: 1. Despite the version number, this is the first draft I've printed. It does shoot. When you do you want to cover the circular hole or the next disc in line will pop out. 2. The firing pin sometimes snaps to one side, jamming. This might be solved by putting a guide into the top of the barrel. Needs more thought. 3. It seems like just pulling the firing pin back far enough to clear the disc gives it a pretty good amount of energy. 4. I'm using some small rubber bands. I'll try with larger ones later. 5. I've only tried the discs with the two small notches in them. The ones with bevels appear to fly better - but I've only shot a few times. 6. In case you're curious, I included my hasty sketch of this part of the mechanism. If you're interested in helping, I've uploaded the OpenSCAD file. I could use some ideas on attaching a handle, getting the firing pin to slide straighter and jam less, magazine for additional discs, how the trigger should work, etc. :) Or, better yet, why not make a derivative?! I think a very similar mechanism could be used to shoot darts like Vik's http://www.thingiverse.com/thing:7512