I have a KWA LM4 and P226 pistol, it is a solid little training gun, I used the Coleman 16.4 oz propane cans with a green gas adapter tip and a little liquid silicone added as mentioned above. Lot cheaper than cans of green gas and works great. As mentioned just make sure your seals/rings are well conditioned and you'll have no problems. Recommend magpuls or ranger plates for the bottom of the gas magazines if you plan on letting them drop free from the weapon ( they hold the gas and tend to break/split if they hit concrete or hardwood from my experience in both pistol and rifle FYI.)