I went ahead and checked how many shots you can get off on 1 fill of Propane in a ATP Magazine, on the NS2 system (For those that still don't know, the NS2 system is amazing when it comes to proper consumption of gas in GBB's)
I was able to get 4 magazines worth of shots before it ran out and would no longer cycle the slide.
1 Magazine = 21 x 4 = 84 Rd's, Pretty impressive I have to note.
I'm curious what the shot capacity on 1 fill is, on something like the KMP9.