From all I've seen, Green Gas is just propane bottled at a lower pressure.
I use the Airsoft Innovations adapter and a few drops of silicone oil made for R/C car's shocks. (Get it at a hobby shop).
The U.S. propane gives all my guns more "kick" and costs next to nothing compared to the Jap stuff.
I'm glad I switched. Now, I don't feel ripped off by a can that costs $11.00, U.S. propane is $2.18/can and cheaper yet with a larger tank and a Harbor Freight small bottle filler.
Who knows? maybe Green Gas will be gone from our local airsoft store's inventory someday, Right Ron? :lol:
Chip