Description
U.S. Army Technical Manual TM 9-1240-312-35 for XM149 Telescope Mount, April 1966, with Change 1
This U.S. Army technical manual covers field-and-depot maintenance for the XM149 Telescope Mount. Issued as TM 9-1240-312-35 in April 1966, this copy has the March 1968 Change 1 update integrated into the manual.
The XM149 was part of the experimental fire-control equipment developed for the XM551, which later entered service as the M551 Sheridan. The mount is identified by Federal Stock Number 1240-762-9334, later written as National Stock Number 1240-00-762-9334.
This listing is for the technical manual only. It does not include an XM149 or M149 mount, telescope, missile tracker, sighting equipment, weapon, or vehicle.
Manual Coverage
The “35” suffix identifies this as a field-and-depot maintenance publication under the Army technical-manual system used during the 1960s. It was intended for trained personnel performing work beyond routine operator and organizational maintenance.
The manual provides technical guidance related to the XM149 mount’s construction and higher-level servicing. Publications at this level supported inspection, troubleshooting, disassembly, cleaning, repair, assembly, adjustment, optical alignment, testing, and final inspection.
March 1968 Change 1
This manual includes the March 1968 Change 1 update. The revised material has been integrated with the original April 1966 publication rather than supplied only as a separate change sheet. This gives the manual added value as a working reference that reflects Army updates made during the early service period of the Sheridan.
About the XM149 Telescope Mount
The XM149 was more than a mechanical bracket. It was a sealed optical, electrical, and mechanical assembly designed to hold the gunner’s articulated telescope and the infrared missile tracker. Its checksight system allowed the tracker to be aligned with the telescope.
The mount included a telescope-locking mechanism, ERROR and ALIGN controls, azimuth and elevation adjustments, optical components, electrical circuits, and a checksight lamp. Its sealed optical section was filled with dry nitrogen to help prevent moisture and internal fogging.
The experimental XM149 was developed alongside the XM119 Articulated Telescope for the XM551 vehicle program. After standardization, the mount became the M149 under military part number 10527950. The standardized mount supported the M119 and later M127 Articulated Telescopes.
Fire-Control Application
The XM149 was installed coaxially with the XM551’s 152mm gun-launcher. This location kept the telescope and tracker aligned with the main weapon as it moved through elevation and depression.
The fire-control system supported conventional 152mm ammunition and the MGM-51 Shillelagh guided antitank missile. The articulated telescope provided the gunner’s direct-fire view, while the tracker followed the missile’s infrared signal. Accurate alignment between the telescope, tracker, mount, and gun-launcher was essential to the system’s operation.
Historical Background
TM 9-1240-312-35 was published while the Sheridan and its advanced fire-control equipment were still entering production. The “XM” prefix shows that the mount was documented in an experimental or pre-standardized form. Its April 1966 date places the manual just before the M551 entered U.S. Army service in 1967.
The March 1968 Change 1 was issued as the Army gained early experience with the new vehicle and its equipment. Sheridans entered combat in Vietnam in 1969. The Army later standardized the XM149 as the M149 and published TM 9-1240-312-34 for the M149 Telescope Mount in May 1973.
Publication Details
- Manual number: TM 9-1240-312-35
- Original publication date: April 1966
- Integrated update: Change 1, March 1968
- Subject: XM149 Telescope Mount
- Later standardized designation: M149
- Federal Stock Number: 1240-762-9334
- Standardized M149 part number: 10527950
- Manual type: Field-and-depot maintenance
- Associated experimental telescope: XM119
- Documented vehicle program: XM551, later standardized as the M551 Sheridan
- Weapon system: 152mm gun-launcher and MGM-51 Shillelagh missile
- Item included: Technical manual only
Collector and Research Value
This manual is a specialized addition to a U.S. Army technical-publication, military-optics, or armored-vehicle collection. Its XM149 designation and integrated Change 1 make it especially useful for studying the development and early service history of the M551 Sheridan fire-control system.
Ideal For
- U.S. Army technical-manual collections
- XM551 and M551 Sheridan research
- XM149 and M149 Telescope Mount research
- XM119 and M119 telescope restoration references
- Vietnam War armored-vehicle displays
- MGM-51 Shillelagh fire-control research
- Experimental Cold War equipment collections
- Museum and archival collections
Approx length 8", Approx width 10", Approx height .25", Approx weight .5lbs.
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