As Wildcard mentioned, go CO2 or go home!
Not only is propane grossly underpowered but in an indoor environment stinks the place up real quick. I'd much rather under charge with CO2 in the 350-400psi than use propane again.
Propane 40's go pop.
CO2 40's are a heck of a lot more satisfying!
People can hear them from a long ways away and sometimes my team checks in over comms, after I've unloaded a few rounds, asking if I need reinforcements. Most times than not, the reply usually goes "No, I'm good. Most of them are dead, all the rest got scared and ran off!".