Possibly the plunger washer. the spring pushes a plunger, which builds up the pressure, if it is not sealing, possibly needs replaced, Most firearm dealers will be able to do it for you. Make sure that you have it covered while outside, even walking to a car. Illegal otherwise. Possible to do it your self, I did my rifle, But different makes, come apart slightly different, Would be impossible or very difficult at least to explain.
SD, June 2011
