Open Source Disc Shooter

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