Abstract: Perforating gun automatic release mechanism wherein the perforating gun is linked to the drilling string by a coupling member. The coupling member includes a plurality of collet fingers, by which said coupling member is attached to the drilling string. The heads of the collet fingers, when inserted into the bottom of the drilling string engage a circumferential groove therein. A slidable locking sleeve, coaxially disposed within the coupling member prevents the inward radial movement necessary for the collet finger heads to disengage the groove. The locking sleeve sits on a slidable piston, which is contained inside the coupling member on top of the explosive charge which detonates the perforating gun. Upon detonation, the resulting shock wave traveling upward pushes the piston and locking sleeve to a position where the collet finger heads are free to disengage the groove, which the weight of the perforating gun then causes, dropping the gun, coupling member and all attachments away from the drilling string.