If you want to see pneumatic shooting at its best, check this out:
http://www.youtube.com/watch?v=cdzpC...&lf=plpp_video
close up CAD rendering of the robot:
http://www.teamtitanium.org/images/09botfull.jpg
I got to see this robot up close when it was in use for Lunacy, it was a really beautiful job!