A syringe is received within a housing, the syringe having a bore terminating at a forward end in a hypodermic needle and at a rearward end in a flared opening in which a bung having a bore surrounded by a skirt is insertod. A drive element has a forward end consisting of a substantially flat annular region that bears upon the skirt of the bung and surrounds a conical middle region that is received in the bore of the bung. An actuator advances the drive element so as to advance the bung and discharge the contents through the needle. The opening in the rear of the synnge is flared by being provided with a radius. The combination of the radius at the opening and the projecting conical middle region of the drive element allows misalignments of the two to be managed during automated assembly.