A machining tool assembly for manufacturing a firearm lower receiver includes a first and second side jig which are configured to be disposed on opposite sides of the firearm lower receiver and configured to removably attach to one another securing the firearm lower receiver therebetween. A drill block jig is removably attachable to the first and second side jigs disposed above the top surface of the firearm lower receiver, wherein the drill block jig comprises a plurality of through holes. A template spacer jig is removably attachable to the first and second side jigs disposed above the top surface of the firearm lower receiver, wherein the template spacer jig comprises a spacer aperture disposed through a template spacer thickness. A first and second pocket templates are removably attachable and disposed onto the template spacer jig. A router support plate is disposed onto either the first or second pocket templates.