A grease gun, in one preferred embodiment, wherein the grease containing portion of the cartridge consists principally of transparent plastic material, wherein the cartridge stands alone without a surrounding supporting metal barrel, wherein the cartridge has an air vented bottom end and an open top end which is non-removably fixed to the grease inlet portion of a pumping head, wherein the pumping head body including the pumping handles is composed of a single plastic molding, wherein the cartridge has no pressurizing spring and piston and no grease compression rod, wherein ambient air pressure is utilized to load the head, wherein valving structures in the head are molded of plastic material, wherein the valving structures are positioned in the head to allow self priming of the pumping structure, and whereby the gun components are easy to assemble, are light weight, and are easy to use.