Description
Technical Manual (TM 9-1240-278-35) for M45/T151E1 Optical Bore Sight August 1960
Technical Manual (TM 9-1240-278-35) for M45/T151E1 Optical Bore Sight – August 1960
Item Overview
This August 1960 U.S. Army technical manual provides direct-support, general-support, and depot-maintenance instructions for the M45/T151E1 Optical Bore Sight.
The M45 was a portable optical instrument used to check the alignment between a mortar tube and its sight unit. It helped maintenance personnel find and correct errors in elevation and deflection.
This listing is for the technical manual only. It does not include an M45 bore sight, carrying case, mortar sight, tools, or replacement parts.
Purpose of the M45 Optical Bore Sight
The M45 attached to the outside of a mortar tube using adjustable straps and clamps. Machined V-shaped surfaces positioned the instrument in line with the tube.
The bore sight was aimed at a distant reference point and compared with the mortar’s regular sight unit. A difference between the two indicated an error in elevation or deflection. The mortar sight could then be adjusted to match the actual position of the tube.
The M45 was an inspection and calibration instrument. It was not the sight normally used to aim the mortar during a firing mission.
Historical Background
The M45 was developed during the 1950s as the U.S. military improved its mortar sights and maintenance equipment. The T151E1 designation reflects the system’s development history before or during standardization as the M45.
Its adjustable mounting system allowed the basic bore-sight design to work with mortar tubes of different diameters. The M45 series later supported several generations of U.S. mortar equipment, including 81mm and 120mm systems.
Published in August 1960, this manual documents the early maintenance procedures for a Cold War optical instrument that remained useful for decades.
Manual Contents
TM 9-1240-278-35 covers advanced maintenance and repair of the M45/T151E1. Subjects include:
- Description and operating principles
- Inspection and troubleshooting
- Disassembly and reassembly
- Cleaning and repair procedures
- Elbow-telescope maintenance
- Body, clamp, and strap components
- Level-vial inspection and adjustment
- Optical alignment and calibration
- Final inspection and performance testing
- Required maintenance tools and equipment
These procedures helped return damaged or inaccurate bore sights to required military standards.
Identification
- Manual number: TM 9-1240-278-35
- Publication date: August 1960
- Covered equipment: M45/T151E1 Optical Bore Sight
- Manual type: Direct-support, general-support, and depot maintenance
- Equipment category: Mortar sight inspection and alignment equipment
- Primary purpose: Detecting and correcting elevation and deflection errors
Collector and Research Value
This manual is a valuable reference for inspecting, repairing, and restoring early M45 bore-sight equipment. Its August 1960 publication date also gives it strong value for Cold War mortar and military-optics collections.
Ideal For
- M45 optical bore-sight restoration
- T151E1 equipment research
- U.S. mortar restoration projects
- Military-optics collections
- Cold War equipment displays
- Museum and technical-library collections
Approx length 8", Approx width 10", Approx height .2", Approx weight .2lbs.
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