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Arsenal | M42A1 ‘Duster’ Anti-Aircraft Gun

By Carl O. Schuster
December 2018 • Vietnam Magazine

Deeply loved for its firepower, the M42 “Duster” self-propelled anti-aircraft gun arose as a replacement for the M19 self-propelled anti-aircraft gun developed in World War II. The M42 employed a slightly expanded variant of the M19 turret mounted on the M41 Walker Bulldog light tank chassis. The Duster’s 500-horsepower gasoline engine, broad tracks and light weight gave it exceptional mobility in South Vietnam’s soft soil and uneven ground. 

The M42’s twin 40mm Bofors cannons fired two rounds per second each, delivering devastating firepower, and its single .30-caliber M1919A4 Browning machine gun or 7.62 mm M60 machine gun provided a close-in punch. 

Although the Duster’s welded steel construction and 25 mm armor protected the drive train and driver from small-arms fire and shell fragments, its open turret left the crew exposed to enemy action. Another concern was the vehicle’s dangerously flammable gasoline. Nonetheless, the M42A1 remained a prized asset for artillery bases and troop convoy commanders.

General Motors Corp. produced 3,700 Dusters between 1952 and 1960. By 1963, however, the Army considered the M42 ineffective against jet aircraft and removed them from all but one active duty unit. After U.S. combat troops went to Vietnam in 1965, the Army reactivated three M42 air defense artillery battalions to counter possible attacks from North Vietnamese aircraft. In November 1966 the 1st ADA Battalion, 44th Field Artillery Regiment, was the first to arrive in-country. 

When the threat of North Vietnamese air attacks never materialized, the Dusters soon turned their guns on enemy ground forces. Their high ground clearance made them mine resistant, and the 40 mm cannon was effective against field fortifications.

More than 200 Dusters served in Vietnam, seeing action along the Demilitarized Zone, in relief of Marine base at Khe Sanh in early 1968, at key engagements in the Central Highlands and in defense of Saigon. When the ADA battalions eventually withdrew, they turned their M42s over to the South Vietnamese. The last M42 was retired from U.S. service in 1986, but some remained active with Vietnam and American allies into the 1990s.

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