Ok this is really pissing me off. I really want to get a glock 18c gbb but half the websites i see say it uses 134a gas and the other half say it uses green gas.

Please TELL ME!! which gas does it use!!!

christ boy, calm yourself down a bit. either can be used, but the best and easiest is to get yourself an AI propane adaptor and run it on propane. although if you're using it on a glock 18c, you better upgrade your slide, outer barrel and recoil spring to metal or you're gonna have that slide crack in no time.