The M42 40 mm Self-Propelled Anti-Aircraft Gun, or "Duster," is an American armored light air-defense gun built for the United States Army from 1952 until December 1960, in service until 1988. Production of this vehicle was performed by the tank division of the General Motors Corporation. It used components from the M41 light tank and was constructed of all-welded steel.
A total of 3,700 M42s were built. The vehicle has a crew of six and weighs 22,500 kg (49,500 lb) fully loaded. Maximum speed is with a range of 100 miles (160 km). Armament consists of fully automatic twin 40 mm M2A1 Bofors, with a rate of fire of 2×120 rounds per minute (rpm) enabling nearly 85 seconds of fire time before running out of ammo, and either a .30 caliber Browning M1919A4 or 7.62mm M60 machine gun. The 500 hp, six-cylinder, Continental (or Lycoming Engines), air-cooled, gasoline engine is located in the rear of the vehicle. It was driven by a cross-drive, two-speed Allison transmission.
Although the M42 Duster was initially designed for an anti-aircraft role, it proved to be effective against unarmored ground forces in the Vietnam War.
Development
During the course of the Korean War, the U.S. Army decided to phase out all vehicles based on the M24 Chaffee chassis, such as the M19 Multiple Gun Motor Carriage 40 mm Anti-Aircraft, in favor of designs that utilized the chassis of the M41. Since the 40 mm guns were still seen as an effective anti-aircraft weapon, a modified version of the gun mount used in the M19 was mounted in a redesigned turret to accommodate the larger turret ring of the M41 and designated as the M42.
Initially, the 40 mm guns were aimed with the assistance of a radar fire control system housed in a secondary vehicle of similar design but this idea was scrapped as development costs mounted.
Service history
Production of the M42 began in early 1952 at GM's Cleveland Tank Plant. It entered service in late 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 December 1960 with 3,700 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 fielding 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, except for the 4th Battalion, 517th Air Defense Artillery Regiment in the Panama Canal Zone, which operated two batteries of M42s into the 1970s.
Vietnam War
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 South Vietnam, the Army began recalling M42A1s back into active service and organizing them into air defense artillery (ADA) battalions. Starting in the fall of 1966, the U.S. Army deployed three battalions of Dusters to South Vietnam, each battalion consisting of a headquarters battery and four Duster batteries, each augmented by one attached Quad-50 battery and an artillery searchlight battery.
Despite a few early air kills, 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 because it turned the enemies into dust) was soon found to excel in ground support. The 40 mm guns proved to be effective against massed infantry attacks. According to an article that appeared in Vietnam Magazine:
Units
Most of the Duster crew members had their AIT training in the 1st Advanced Individual Training Brigade (Air Defense) at Fort Bliss, Texas. Some of the Duster NCOs had received training at the Non Commissioned Officers Candidate School which was also held at Fort Bliss, Texas.