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The self-propelled M42 Duster, sweeper, is a version of the American light tank M41 Walker Bulldog, turret armed with two 40mm cannons Bofors manufactured under license .


The M42 Duster series is based on the M41 "Walker Bulldog" chassis by fitting the twin gun mount inside the hull turret ring.
Id m42duster 4id pettit 239 20051202

M-42 Duster at 4th Infantry Division Museum, Ft. Hood, Texas, 2 December 2005.

Three models were standardized, M42 produced from 1951-1953, the M42A1 standardized in 1956, and M42A2, all with the nomenclature "Carriage, Self-propelled, Anti-aircraft, Twin 40mm, 25-ton, (Duster)."

The interior of the M42 Duster is divided into three areas: driving compartment at the front, stowage compartment in the center, and engine compartment in the rear. The driving compartment contains the driving controls and instruments. The seats for the driver and commander-radio operator are in the driving compartment. The stowage compartment serves as a base for the gun mount with space for 12 boxes of 40-mm ammunition. The engine compartment houses the main engine, auxiliary generator and engine, transmission, and fuel tanks. The gunner, squad leader, and cannoneer ride in the gun mount. The squad leader commands, via the intercommunications set AN/VIC-1, either from the commander's seat or the gun mount.

The 25 ton Duster is powered by a Lycoming AOSI-895-5 6 cyl. fuel injected 500 hp engine.

Operational HistoryEdit

Production of the M42 began in early 1952 at GM's Cleveland Tank Plant. It entered service in 1953 and replaced a variety of different anti-aircraft systems in armored divisions. In 1956, the M42 received a new engine and other upgrades along with other M41 based vehicles, becoming the M42A1. Production was halted in Dec. 1959 with 3700 examples made during its production run. Sometime in the late 50s, the U.S. Army reached the conclusion that anti-aircraft guns were no longer viable in the jet age and began field a self-propelled version of the HAWK SAM instead. Accordingly, the M42 was retired from front line service and passed to the National Guard with the last M42s leaving the regular Army by 1963.

Vietnam WarEdit

Id m42duster 4id pettit 246 20051202

A close-up in the two Bofors AA cannons

Unfortunately, the HAWK missile system performed poorly in low altitude defense. To ensure some low altitude anti-aircraft capability for the ever increasing amount of forces fielded in Vietnam, the Army began recalling M42A1s back into active service and organizing them into air defense artillery (ADA) battalions. Three M42A1 equipped ADA battalions were sent to Vietnam, the first arriving in late 1966.

Despite a few air kills early, the air threat posed by North Vietnam never materialized, and ADA crews found themselves increasingly involved in ground support missions. Most often the M42 was on point security, convoy escort or perimeter defense. The "Duster" (as it was called by U.S. troops in Vietnam) was soon found to excel in ground support. The rapid firing 40mm guns could devastate massed infantry attacks or sweep away guerrillas hiding in the jungle with equal ease. The Duster was both feared and hated by the Viet Cong and parked M42s attracted an inordinate amounts of attention from saboteurs.

Post VietnamEdit

The last M42A1 equipped ADA units left Vietnam in 1972 and the Duster was returned to the National Guard. The U.S. Army maintained multiple National Guard M42 battalions as a corps level ADA asset until the system was retired in 1988.


  • M42
  • M42A1: received the AOSI-895-5 engine.
  • Type 64: Taiwanese light tank variant produced by mating turrets of M18 tank destroyer onto M42 hulls.


"The Duster" M-42A1 self-propelled 40mm anti-aircraft gun system


6 [usually 4 in actual combat conditions]


Twin 40mm cannon, one 7.62 mm machine-gun


Main anti-aircraft: 480 rounds

Types: Armor-Piercing Tracer and High Explosive Tracer


All-welded steel - thickness: 9mm-25mm (0.35-0.99 in)


Length (including guns): 20 ft 10in (6.356m)

Length (hull): 19 ft 1in (5.819m)

Width: 10 ft 7in (3.225m)

Height: 9 ft 4in (2.847m)


Combat: 49,500 lbs (22.452 kg)

Ground pressure

9.24 lb/in2 (0.65 kg/cm2)


Continental (or Lycoming) six-cylinder air-cooled gasoline engine developing 500 bhp at 2,800rpm

Fuel Capacity

140 US gallons (530 liters)


Road speed: 45 mph (72 km/h)

Range: 100 miles (161 km)

Vertical obstacle: 2 ft 4in (0.711m)

Trench: 6 ft 4in (1.828m)

Gradient: 60%

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