Description
Technical Manual (TM 9-1240-278-20P) for M45/T151E1 Optical Bore Sight October 1969 FSN 1240-690-8811
Technical Manual (TM 9-1240-278-20P) for M45/T151E1 Optical Bore Sight W/E, FSN 1240-690-8811 – October 1969
Item Overview
This October 1969 U.S. Army technical manual is the organizational-maintenance repair-parts and special-tools publication for the M45/T151E1 Optical Bore Sight W/E.
The complete equipment configuration is identified by FSN 1240-690-8811. The abbreviation “W/E” means “with equipment,” referring to the bore sight as issued with its associated components and equipment.
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 was a portable optical instrument used to check the alignment of a mortar tube and its sight unit. It attached to the outside of the tube with adjustable straps and clamps.
Machined V-shaped surfaces positioned the bore sight in line with the mortar tube. The crew aimed the instrument at a distant reference point and compared its view with the mortar’s regular sight unit.
Any difference showed an error in elevation or deflection. The sight could then be adjusted so its settings matched the actual direction and elevation of the mortar tube.
The M45 was used for inspection and calibration. 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 preserves the system’s earlier development identity.
Its adjustable mounting system allowed the basic bore-sight design to work with mortar tubes of different diameters. The M45 series remained useful through several generations of U.S. mortar equipment, including later 81mm and 120mm systems.
This October 1969 edition was published during the Vietnam War era. It reflects continued Army support for a proven optical alignment system that had entered service about a decade earlier.
Manual Contents
TM 9-1240-278-20P helped maintenance personnel identify authorized components and equipment. Its contents include:
- Major bore-sight assemblies
- Elbow-telescope components
- Body and telescope-clamp parts
- Strap and clamp assemblies
- Level and adjustment components
- Mounting hardware
- Associated equipment
- Exploded assembly illustrations
- Federal stock numbers and part numbers
- Quantity and application information
- Special tools and maintenance equipment
- Numerical parts indexes
The illustrated-parts format is also useful for identifying incomplete or disassembled M45 equipment sets.
Identification
- Manual number: TM 9-1240-278-20P
- Publication date: October 1969
- Covered equipment: M45/T151E1 Optical Bore Sight W/E
- Federal Stock Number: 1240-690-8811
- Manual type: Organizational-maintenance repair parts and special tools list
- Equipment category: Mortar sight inspection and alignment equipment
- Primary purpose: Detecting elevation and deflection errors in a mortar sight
Collector and Research Value
This manual is a valuable reference for identifying M45 bore-sight parts and associated equipment. It also documents Army support of mortar-alignment instruments during the Vietnam War era.
Ideal For
- M45 optical bore-sight restoration
- T151E1 equipment research
- FSN 1240-690-8811 equipment identification
- U.S. mortar restoration projects
- Military-optics collections
- Museum and technical-library collections
Approx length 8", Approx width 10", Approx height .15", 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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