Downhole automatic tool release and method of use

A release tool adapted to be connected between a perforating gun and a tubing for releasing the perforating gun from the tubing after detonation of the perforating gun, the tool including a housing in connection with the tubing, the housing having an axial bore; an axially shiftable member in connection between the housing and a perforating gun; a seal member positioned in the axial bore of the housing, the axially shiftable member positioned through the seal member; a frangible member maintaining the axially shiftable member in connection between the housing and the perforating gun until the frangible member is shatter disconnecting the shiftable member; and a mechanism for equalizing the pressure across the seal member after the axially shiftable member is disconnected allowing the perforating gun to separate from the housing.