A mold assembly for forming a piston and method of molding a piston therewith includes a pair of mold halves moveable toward and away from one another along a linear path that is substantially perpendicular to a longitudinal central axis of the piston between an engaged position to provide at least a portion of a mold cavity for forming an outer periphery of the piston and a disengaged position to allow extraction of the piston from the mold cavity. The assembly also has a pair of cooling gallery mandrels moveable along a linear path into an engaged position between the pair of mold halves to form an undercut cooling gallery of the piston. The pair of cooling gallery mandrels are movable to a disengaged position to allow extraction of the piston vertically along the axis.