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|Type||Self-propelled anti-aircraft gun|
|Place of origin||United States|
|Weight||24.8 t (loaded)|
|Length||5.82 m (19 ft 1 in)|
|Width||3.23 m (10 ft 7 in)|
|Height||2.85 m (9 ft 4 in)|
|M2A1 40 mm twin anti-aircraft gun with 336 rounds|
|1 × M1919A4 7.62 mm machine gun|
|Engine||6-cylinder air-cooled gasoline
500 hp (375 kW)
|160 km (99 mi)|
|Speed||72 km/h (45 mph)|
The M42 40 mm Self-Propelled Anti-Aircraft Gun, or "Duster," is an armored light air-defense gun built for the U.S. Army from 1952 until December 1959. 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 45 mph with a range of 100 miles. Armament consists of fully automatic twin 40 mm M2A1 Bofors, with a rate of fire of 2x120 rounds per minute (rpm) 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, 2-speed Allison transmission.
Although the M42 Duster was initially designed for an anti-aircraft role, it proved highly successful when used in the Vietnam War against unarmored ground forces.
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 Gun Motor Carriage 40mm Anti-Aircraft, in favor of designs that utilized the chassis of the M41. Since the 40mm guns were still seen as an effective anti-aircraft weapon, the turret of the M19 was simply mounted to the M41 chassis with few changes except a partial redesign to accommodate the larger turret ring of the M41 and designated as the M42.
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 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 Bn, 517th Air Defense Artillery Regiment in the Panama Canal Zone, which operated two batteries of M42s into the 1970s.
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. Starting in the fall of 1966, the U.S. Army deployed three battalions of Dusters to the Republic of Vietnam, each battalion consisting of a headquarters battery and four Duster batteries, and 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) was soon found to excel in ground support. The 40mm guns proved to be effective against massed infantry attacks.
"M-55s and M-42s were old pieces of equipment that needed a lot of maintenance and required hard-to-get spare parts. The gasoline-powered Dusters were particularly susceptible to fires in the engine compartment. Thus, despite its cross country capability, it was not wise to use the Duster in extended search and destroy operations in heavy jungle terrain because of excessive wear on engines, transmissions and suspensions.
"On the plus side, the Duster was essentially a fairly simple piece of machinery on which the crews could perform maintenance. Better yet, the Duster's high ground clearance and excellent suspension-system design gave it an ability to withstand land mine explosions with minimal crew casualties.
"Although the Duster's 40mm shell had a terrific blast and fragmentation effect, it also had a highly sensitive point-detonating fuse that limited effectiveness in heavy vegetation. Under those conditions, the better weapon was the Quad, because the heavy .50-caliber projectile could easily punch through cover that would detonate the Duster's 40mm shell too early for it to be effective. At long ranges, however the 40mm shell was far more useful, particularly against field formations. The Duster also was able to deliver indirect fires by using data from field artillery fire-directions centers."
"Soldiers of the 1/44th Artillery and their Marine counterparts in I Corps set the pattern of Quad and Duster operations. Because of an early scarcity of armored-combat vehicles, M-42s were first used as armor. Often thankful men quickly learned the value of high volumes of 40mm and .50-caliber fire, both in the field and perimeter defenses. Quads beefed up the defenses of remote fire bases, while Dusters accompanied both supply and tactical convoys along contested highways to break up ambushes. Dusters of Battery C, 1/44th Artillery, led the task force of Operations Pegasus that broke the siege of Khe Sanh in April 1968. Dusters and Quads provided critical final-protective fires throughout Vietnam during the Tet offensive and later took part in Operation Lam Son 719. Whenever fire support was needed, M-42s and M-55s could be found."
- - Charles E. Kirkpatrick, in "Arsenal", Vietnam magazine
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 Offices Candidate School which was also held at Fort Bliss, Texas.
The 1st Battalion of the 44th Artillery was the first ADA battalion to arrive in Vietnam on November 1966. A self-propelled M42A1 Duster unit the 1st of the 44th supported the Marines at places like Con Thien and Khe Sanh as well as Army divisions in South Vietnam's rugged I Corps region. The battalion was assigned to First Field Force Vietnam (IFFV) and was located at Dong Ha. In 1968 it was attached to the 108 Artillery Group (Field Artillery). Attached to the 1/44th was G Battery 65th Air Defense Artillery Quad -.50 caliber machine guns and G Battery 29th Artillery Searchlights. The 1/44th served along side with the 3rd Marine Division along the DMZ in ICORP thru December 1971.
Sgt., E-5 Mitchell W. Stout was a member of C Battery, 1st Battalion of the 44th Artillery. He was awarded the Medal of Honor. Also killed in this action was SP-4 Terry Lee Moser, of Barto, Pennsylvania. He was also assigned to C Battery, 1st Battalion, 44th Artillery.
The second Duster battalion to arrive in Vietnam was the 5th Battalion of the 2d Air Defense Artillery (5/2d). Activated in June 1966 it arrived in Vietnam in November of 1966 and was diverted to III Corp, Second Field Force (IIFFV) and set up around Bien Hoa airfield. Attached units were D Battery 71st Air Defense Artillery Quad - .50 caliber machine guns and I Battery 29th Artillery Searchlights. The "Second First" served the southern Saigon region thru mid 1971. D-71st Quads remained active thru March 1972.
The third Duster battalion to arrive was the 4th Battalion of the 60th Air Defense Artillery (4/60th). Activated in June 1966 it arrived in Vietnam in June 1967 and set up operations in the Central Highlands based out of An Khe ('67-70) and later Tuy Hoa ('70-71). Attached units were E Battery 41st Artillery Quad - .50 caliber machine guns and B Battery 29th Artillery Searchlights (which were already in country since Oct 1965). Members of these units not only covered the entire Central Highlands of IFFV, but assets also supported firebases and operations along the DMZ to the north and Saigon to the south.
Each Duster Battalion had four line battery's (A,B,C,D) and a headquarters battery. Each battery had two platoons (1st, 2nd) which contained four sections each containing a pair of M42A1 Dusters. At full deployment there were roughly 200 M42 Dusters under command throughout the entire war. The Duster and Quads largely operated in pairs at firebases, strong points and in support of engineers building roads and transportation groups protecting convoys. At night they protected the firebases from attack and were often the first targets of enemy sappers, rockets and mortars. Searchlights and searchlight jeeps operated singularly but often in support of a Duster or Quad section at a firebase.
Between the three Duster battalions and the attached Quad-50 and Searchlight battery's over 200 fatalities are recorded. 
The three M42A1 equipped ADA units (1/44th, 4/60th & 5/2d) deactivated and left Vietnam in late December 1971. Most if not all of the in-country Dusters were turned over to ARVN forces. Most of the training Dusters at Ft.Bliss were returned to various National Guard units. The U.S. Army maintained multiple National Guard M42 battalions as a corps level ADA asset until the system was retired in 1988.
- United States of America: US Army, US National Guard
- Germany, Replacement by SPAAG "Gepard" starting in 1976.
- Greece: Hellenic Army, from surplus German stocks.
- Japan: Japan Ground Self Defense Force
- Jordan: Phased out
- Lebanon: 15 M42A1 Dusters in service with the Lebanese Army (1958–1984), passed on to the Army of Free Lebanon, Lebanese Arab Army, Tigers Militia, Guardians of the Cedars, Kataeb Regulatory Forces, Lebanese Forces
- Pakistan: Pakistan Army, 123 In Service.
- Taiwan: Republic of China Army, Republic of China Marine Corps
- Thailand: Royal Thai Army
- Turkey: Will be replaced by a new FNSS 2x35mm ACV
- Venezuela: Venezuelan Army, retired from service in 1989, AMX-13/M41E1 Ráfaga since 1998
- M42A1: received the AOSI-895-5 engine (500 hp).
- Type 64: Taiwanese light tank variant produced by combining turrets of decommissioned M18 tank destroyers with surplus M42 hulls. Compartments over the track guards for spare Bofors gun barrels were replaced with storage boxes of the stock M41 tank. One battalion worth (50+) of conversions were made.
- AMX-13/M41E1 Ráfaga: Venezuelan self-propelled AA gun variant produced by combining turrets of decommissioned M42A1 Dusters towers (M41E1) with surplus AMX-13M51 hulls, with improvements in fire control for night operations and on original chassis. One anti-aircraft battery worth of +/-10 conversions was made.
ADA Units in Vietnam
- Cole, Frederick (Bill) (30 April 2011). "4th Missile Bn (Hawk-AW) 517th Artillery Panama Canal Zone". www.517thartillery.org. Retrieved 28 June 2011.
- Air Defense Artillery in Vietnam
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