A California Army National Guard crew mans a self-propelled 40mm anti-aircraft gun, likely an M42 'Duster,' during range training. Built on a tracked chassis descended from the M41 Walker Bulldog light tank, the Duster paired mobility with rapid-fire twin 40mm cannon for airfield and convoy defense. Photographs like this one document the routine field exercises that kept citizen-soldiers proficient between periods of active federal service. Project: 218665