I have a gas-powered Airsoft UZI. It does not fire. I noticed the pin on the valve to release the gas (which the trigger should be depressing in order to fire the gun) does not budge. On my other guns I can press it with my finger, but this one I can't even press with a screw-driver. I noticed this little piece of metal in there, and wonder if it is there to prevent the pin from being pressed and is intended to be removed. Any advice?