The gun is rated by amperage, duty cycle and cable length, and those three numbers decide whether it survives production work.
Amperage rating must exceed the output you actually run. A 250 A gun on a machine set to 250 A is at its limit; the same gun run continuously at 200 A lasts far longer. Duty cycle follows the same logic — a 60% duty cycle gun that runs 100% of the time at rated amperage will overheat and fail.
Cable length adds resistance, which shows up as a weaker arc and a hotter cable. Longer guns need heavier cable for the same amperage. Euro-connector guns plug into the feeder; direct-connect guns are specific to a machine brand and feeder type.
Spool guns carry a small spool of wire on the gun itself, which is how aluminium is MIG welded — soft aluminium wire cannot be pushed through a long liner without tangling. Spool guns are also used where a large wire spool cannot reach. Push-pull guns combine a feeder drive at both ends for long-reach aluminium welding.
