Description
U.S. Army Technical Manual TM 9-1290-270-35 for M27 Azimuth Indicator, June 1961
Item Overview
This vintage U.S. Army technical manual covers field and depot maintenance for the M27 Azimuth Indicator. Issued in June 1961, TM 9-1290-270-35 supported trained personnel responsible for repairing and testing this mechanical fire-control instrument. The M27 was used with the M42 and M42A1 twin 40 mm self-propelled antiaircraft guns, commonly called Dusters. This listing is for the technical manual only. It does not include an azimuth indicator, sight, gun, vehicle, or other equipment.
Publication Details
This manual belongs to the Army’s 1290-series publications for miscellaneous fire-control equipment. Its “35” maintenance level placed it above routine crew and organizational service.
- Manual number: TM 9-1290-270-35
- Publication date: June 1961
- Primary subject: M27 Azimuth Indicator
- Equipment type: Mechanical fire-control instrument
- Associated NSN: 1290-00-355-5062
- Manual level: Field and depot maintenance
- Associated vehicles: M42 and M42A1 Duster
- Issuing authority: Headquarters, Department of the Army
- Country of origin: United States
- Item included: Technical manual only
Manual Coverage
TM 9-1290-270-35 was prepared for maintenance work beyond normal crew care. Its technical guidance supported inspection, troubleshooting, disassembly, cleaning, repair, reassembly, adjustment, calibration, and final testing of the M27. This type of publication helped military shops return accurate fire-control instruments to service.
About the M27 Azimuth Indicator
The M27 was a mechanical indicator connected to the weapon mount’s traverse system. It showed the horizontal direction, or azimuth, of the rotating gun mount in relation to the vehicle. This allowed a crew to set and repeat an assigned direction when the target could not be engaged by direct sight. On the M42 series, the M27 supported indirect fire while the M38 computing sight and related sights were used for direct tracking and engagement.
M42 Duster Weapon-System History
The M42 was developed during the Korean War era to replace the older M19 twin 40 mm gun carriage. It used major parts from the M41 light-tank chassis and carried two 40 mm M2A1 automatic guns in an open-topped rotating mount. Production began in 1952, and about 3,700 M42 and M42A1 vehicles were built. The upgraded M42A1 received a fuel-injected engine and other improvements. The Duster was designed to give armored and mechanized units mobile protection against low-flying aircraft.
History of Use
The June 1961 publication date places this manual near the end of the M42’s first period of regular Army service. Guided missiles were replacing gun-based air defenses, and many Dusters moved to Army National Guard units. The M42A1 returned to active combat service in Vietnam beginning in 1966. Because enemy air attacks were limited, crews used the twin 40 mm guns for convoy escort, perimeter defense, road security, and infantry support. Their rapid fire was especially effective against exposed troops and fortified positions. Duster units served in South Vietnam through 1971, and the vehicle remained with National Guard and allied forces for many years.
Collector and Research Value
This manual documents a specialized part of the M42 Duster’s fire-control system. It is useful for studying Cold War air-defense equipment, mechanical gun-laying instruments, indirect-fire methods, and Army maintenance practices. It can also support museum research, vehicle restoration, and technical-manual collections.
Condition
This vintage military technical manual may show cover wear, edge wear, folds, yellowing, stains, writing, stamps, punched holes, loose pages, or other signs of age and storage. Printing details and condition may vary between available copies. Please check the pictures for the general condition of the item.
Ideal For
This specialized manual is well suited for collectors, restorers, researchers, and exhibits covering American air-defense vehicles and Cold War fire-control equipment.
- U.S. Army technical-manual collections
- M42 and M42A1 Duster restoration
- M27 Azimuth Indicator research
- Twin 40 mm gun-system displays
- Vietnam War vehicle exhibits
- Cold War fire-control studies
- Museum and archival collections
Approx length 8", Approx width 10", Approx height .2", Approx weight .2lbs.
Pictures are stock images of our inventory. Unless otherwise noted, you will not be receiving the exact item shown in the pictures. The pictures are representative of the item’s general condition. The item you receive might be slightly better, or worse, condition than was shown in the pictures.
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