Never heard of using propane for airsoft.
Hm.
that's because local stores and supermarkets only rarely sell actual intermediate- to pro-level airsoft sporting gear-- they mainly only sell cheap spring guns, low-quality AEG's and CO2 non-blowbacks; things that appeal to the kind of people who just want to have fun in their backyards with friends
I've heard that some milsim/pro players even look down on people who use CO2 because of it's inferiority to green gas/propane(same thing basically) in airsoft :|