Can anyone make cd shootter?

That's mine first crossbow :) Currently it does not have some power because of rubber band. So I'm asking for some advice what to put on front, but the condition is that it has to be spring or some rubber band. I made front part easy mountable so I can have more extensions. Thanks in advice :)

http://www.kickstarter.com/projects/11447722/rubber-band-machine-gun-0 They are offering preorders on this beast completed with a fast charger for 130 USD. Looks cool what do you think? :) EDIT: I love how he uses a string as a trigger mechanism and the loading tool is also very clever.