Description
TM 9-3045 Technical Manual - 40mm M2A1 Dual Automatic Gun and M4E1 Twin Gun Mount used on M42 Duster - October 1956
Item Overview
TM 9-3045 is an October 1956 technical manual for the 40mm M2A1 dual automatic gun and M4E1 twin gun mount. This Army field and depot maintenance publication covers the armament installation associated with the M42 Duster. It is a period reference for studying the paired cannons and the equipment that supported and aimed them.
Identification and Features
Key publication and equipment details include:
- Manual number: TM 9-3045
- Publication date: October 1956
- Cross-listed publication: Air Force TO 11W2-5-2-32
- Maintenance scope: Ordnance field and depot maintenance
- Armament: 40mm M2A1 dual automatic gun
- Mount: 40mm M4E1 twin gun mount
- Documented application: M42 Duster self-propelled antiaircraft gun
Function and Manual Contents
Written for ordnance repair personnel, TM 9-3045 addresses field and depot maintenance of the gun and mount assemblies. Its scope connects cannon maintenance with the supporting and aiming equipment of the installation. This focus makes the publication useful for component identification, maintenance history, and research into the mechanical layout of the Duster's armament.
Documented End-Item Application
The M2A1 dual automatic gun and M4E1 mount formed the main armament installation of the M42 Duster. The two guns shared a rotating mount with positions for the gun crew. Together, they gave the vehicle an antiaircraft armament that could also engage ground targets.
Publication History
This 1956 edition dates from the M42's early Cold War service, before its later combat use in Vietnam. The publication carried both the Army TM 9-3045 designation and Air Force TO 11W2-5-2-32 number. Its title identifies the guns and mount separately, preserving the component names used in military maintenance records of the period.
Equipment History
The twin 40mm installation continued a concept already used on the wartime M19 self-propelled gun. As the Army moved from the M24 Chaffee vehicle family to the newer M41 light tank family, the M42 carried twin 40mm armament onto the newer chassis. This development linked established cannon technology with a new generation of tracked vehicles.
M2A1 Dual Automatic Gun
The M2A1 belonged to the Swedish Bofors 40mm gun family. The U.S. Army had adopted the air-cooled Bofors as the 40mm M1 antiaircraft gun in April 1941. The later dual installation carried that cannon tradition into postwar service. Its guns used automatic loading mechanisms supplied from above by four-round clips. Each cannon had its own loading mechanism, while the mount aimed the pair together.
M4E1 Twin Gun Mount
The M4E1 was the mechanical foundation of the Duster's twin-gun installation. Its open-topped armored structure rested on a ball-bearing race and could turn through a full circle. Powered controls and manual controls allowed the crew to aim the guns. The mount brought the cannon supports, aiming mechanisms, and crew positions together as one assembly, continuing the twin-gun turret layout developed for earlier tracked antiaircraft vehicles.
Parent Weapon-System Background
The M42 Duster was a full-tracked armored air defense vehicle based on the M41 Walker Bulldog chassis family. It was designed to accompany maneuver forces and defend them against low-flying aircraft. Its tracked mobility and rotating gun installation allowed it to move with ground formations. The vehicle entered service during the 1950s, when gun-based air defense served alongside developing surface-to-air missile systems.
History of Use
In Vietnam, Dusters became valuable ground-support weapons, protecting convoys, firebases, and other defended positions. Army air defense history records their support of Marines during the fighting at Hue and the defense of Khe Sanh in 1968. These missions demonstrated how the twin 40mm installation could serve beyond its original antiaircraft role. The M42 family remained in U.S. service until 1988.
Ideal For
This publication suits collections focused on Bofors-derived cannon, powered gun mounts, and Cold War air defense. Its combined coverage is useful for researching the armament as a complete installation and building a technical reference library for surviving Duster equipment.
- Army technical manual collectors
- M42 Duster restoration archives
- M2A1 gun and M4E1 mount researchers
- Bofors 40mm historians
- Cold War and Vietnam War museums
Approx length 6", Approx width 9", Approx height .5", Approx weight 1lbs.
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