A cover for a receiver of a gun that may include an elongated member having a first longitudinal axis, the elongated member including a distal end portion which may include a leading edge which is configured and dimensioned to connect with a gun part, and a proximal end portion which is spaced from the distal end portion along the first longitudinal axis. The elongated member may include a first locking mechanism adjacent the proximal end wall. The first locking mechanism may be secured to a recoil spring guide of the gun. Also, the elongated member may include a second locking mechanism adjacent the distal end portion. The second locking mechanism may be secured to a rear sight base of the gun. The elongated member may include an accessory rail.