Guns are either the push or pull type. The pull gun has drive rolls that pull the welding wire from the wire feeder, and the push gun has the wire pushed to it by drive rolls in the wire feeder itself. Both guns have a trigger switch that controls the wire feed and arc as well as the shielding gas. When the trigger is released, the wire feed, arc, and shielding gas stop immediately. With some equipment, a timer is included to permit the shielding gas to flow for a predetermined time to protect the weld until it solidifies.
Guns are available with a straight or curved nozzle.
The curved nozzle provides easy access to intricate joints and difficult to weld patterns. Shielding gases in the gas metal-arc process are used primarily to protect the molten metal from oxidation and contamination. Other factors must be considered, however, in selecting the right gas for a particular application. Shielding gas can influence arc and metal transfer characteristics, weld penetration, width of fusion zone, surface-shape patterns, welding speed, and undercut tendency. Inert gases, such as argon and helium, provide the necessary shielding because they do not form compounds with any other substance and are insoluble in molten metal.