Somethings wrong with my Spyder VS1, its leaking co2 out of the front handle part? (stick thing under barrel)?

Whenever i put a tank in my VS1 Co2 leaks out of the chamber thing. Its the thing that sticks out forward, it looks like a smaller, second barrel. it screws on and off just like a barrel. Is it the gun itself, maybe the co2 system? or is it the O ring on the "second barrel"? ive tried 3 different tanks that work on other guns but they dont work on my gun