gas problem

I just barely got the umirex walther sg9000 shotgun. I put in the gas for a game and it worked fine. after the game it wasnt shooting very well. it was only shooting like 10 yards instead of its 50 yard range. I pulled of the gas cover and saw the tank. pulled it out and put lube on the top of the next 88g catridge. I put it in in the screw point, it didnt seal and gas started to come out of the trigger, forgrip, pistol grip and pretty much all over making a bubbly nose inside. it is 89 degress F outside. what did I do wrong? it was shooting fine? it says I can send it back for a new one. I just got it yesterday...help me Im not a airsoft expert.

plus there is no O ring to seal, its just flat metal on metal.

Thats your problem right there. You need a O-ring. In a previous life I was a paintballer, and one of the things that guys always told me is to always have an O-ring.

It stops leakage, so that entire game, you were probably draining gas and not knowing it. A game is a long time for gas to spill out, so when you got home, you were probably running on less than nominal gas output, thus the weird range.