Air gun and pressure relief valve therefor

In an air gun having a frame, the frame comprising a pair of mating halves and having an upper and a lower wall, a barrel mounted on the frame, a valve body mounted on the frame above said upper wall and having a pressure reservoir for storing pressurized air, pump means for supplying pressurized air to the pressure reservoir, and firing means for releasing pressurized air from the pressure reservoir to the barrel for propelling a projectile out of the barrel, the improvement comprising a pressure relief valve for preventing the pressure in the pressure reservoir from exceeding a desired maximum pressure, the pressure relief valve comprising a valve housing positioned between said upper and lower frame walls and including a reduced-diameter neck portion which extends through said upper frame wall into an opening in the valve body, an O-ring surrounding the neck portion for providing a seal between the neck portion and the valve body, said valve housing having an inlet communicating with the pressure reservoir, a plunger chamber, and an outlet orifice, a plunger within the chamber, and spring means for resiliently biasing the plunger against the inlet for sealing the inlet until the pressure within the pressure reservoir overcomes the force exerted by the spring means.