You really need to have the gas cylinder gauged. If you dont have anyway of doing it you can send it to me and I can check it and send it back, you pay shipping both ways
You also need to look over the gas screw very carefully. Look for cracks and make sure you have it installed tight. You also need to check to see if it is leaking.
put a piece of tape across the end of it and fire a round, if the tape gets blown off of it is leaking.
also check the gas port in the barrle, make sure it isnt plugged