Abstract: A compact, flexible, lightweight welding gun is provided, including a single outer tubular casing substantially containing all the weld gun components. Concentric disposition of annular fume evacuating passageways between the outer tubular casing and component electrical transmitter elements insulates the external surfaces of the casing from the electrical heat sources within the gun, while cooling gases circulating in the gas passageways promote dissipation of accumulating heat. The improved cooling properties of the gun permit relatively higher levels of current and therefore increased speed of weld bead deposition, while the single conduit structure of the welding apparatus renders it more compact, flexible and lightweight, as well as more maneuverable due to the relatively clean exterior of the gun.