Description
U.S. Army Technical Manual Change 2 for TM 9-1240-312-35, M149 and M165 Telescope Mounts, December 1969
This official U.S. Army publication is Change 2 for TM 9-1240-312-35, the field-and-depot maintenance manual for the M149 and M165 Telescope Mounts. Issued in December 1969, it updated the original technical manual dated April 25, 1966.
The M149 is identified by Federal Stock Number 1240-762-9334. The M165 is identified by Federal Stock Number 1240-178-8440. Both mounts were used with fire-control equipment on the M551 Sheridan.
This listing is for the Change 2 update only. It is not the complete TM 9-1240-312-35 maintenance manual. It does not include an M149 or M165 mount, telescope, missile tracker, sighting equipment, weapon, or vehicle.
Purpose of Change 2
Army technical-manual changes supplied official corrections, revised instructions, and replacement material for an existing publication. Change 2 was intended to be kept with the original April 1966 manual and its applicable earlier updates.
This December 1969 change expanded the manual’s coverage to include both the missile-equipped M149 and the M165 used on Sheridan vehicles without missile capability. It helped maintenance personnel identify and service the correct telescope mount for each vehicle configuration.
About the M149 Telescope Mount
The M149 was a sealed optical, electrical, and mechanical assembly used on M551 Sheridans equipped with the MGM-51 Shillelagh missile subsystem. It supported the gunner’s articulated telescope and the infrared missile tracker while keeping them aligned with the vehicle’s 152mm gun-launcher.
The mount included an internal checksight, ERROR and ALIGN controls, azimuth and elevation adjustments, optical components, electrical circuits, and a telescope-locking mechanism. Its sealed optical section was filled with dry nitrogen to help prevent moisture and internal fogging.
About the M165 Telescope Mount
The M165 was used on M551 Sheridans built without missile capability. On those vehicles, it replaced the M149 because an infrared missile tracker and its related checksight equipment were not required.
The M165 still supported the gunner’s articulated telescope for aiming conventional 152mm ammunition. Army illustrations show it installed beside a modified gun-and-turret control selector and a missile-capability stop that prevented selection of the unavailable missile system.
Fire-Control Application
Both mounts were installed coaxially with the Sheridan’s 152mm gun-launcher. This allowed the telescope to follow the weapon through elevation and depression while providing the gunner with a direct-fire view.
The M149 served vehicles capable of firing conventional ammunition and the MGM-51 Shillelagh guided missile. The M165 served non-missile vehicles that used the gun-launcher only with conventional ammunition. This configuration difference explains why both mounts were added to the same maintenance publication.
Historical Background
The original TM 9-1240-312-35 was issued on April 25, 1966, while the XM551 vehicle and its fire-control equipment were moving from development into production. Change 1 followed in March 1968 as the Army began fielding the standardized M551 Sheridan.
Change 2 was issued in December 1969, during the Sheridan’s first year of combat service in Vietnam. Some production vehicles were completed without the Shillelagh missile subsystem, which required the M165 mount and related control changes. This update documents the Army’s need to maintain both missile-capable and conventional-only Sheridan configurations.
Publication Details
- Publication type: Technical Manual Change 2
- Applicable manual: TM 9-1240-312-35
- Change date: December 1969
- Original manual date: April 25, 1966
- Previous update: Change 1, March 1968
- Primary subjects: M149 and M165 Telescope Mounts
- M149 Federal Stock Number: 1240-762-9334
- M165 Federal Stock Number: 1240-178-8440
- Original manual type: Field-and-depot maintenance
- Documented parent system: M551 Sheridan
- M149 application: Vehicles with missile capability
- M165 application: Vehicles without missile capability
- Supported weapon: 152mm gun-launcher
- Related missile system: MGM-51 Shillelagh
- Item included: Change 2 update only
Collector and Research Value
This Change 2 update is a specialized addition to a U.S. Army technical-publication, military-optics, or armored-vehicle collection. It is useful for completing a TM 9-1240-312-35 manual set and for studying the different fire-control configurations used on Vietnam War-era M551 Sheridans.
Ideal For
- TM 9-1240-312-35 manual sets
- U.S. Army technical-manual collections
- M149 and M165 Telescope Mount research
- M551 Sheridan restoration references
- Vietnam War armored-vehicle displays
- MGM-51 Shillelagh fire-control research
- Cold War military-optics collections
- 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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