Technical Manual (TM 9-1240-278-20P) for M45/T151E1 Optical Bore Sight June 1960

Technical Manual (TM 9-1240-278-20P) for M45/T151E1 Optical Bore Sight June 1960

Technical Manual (TM 9-1240-278-20P) for M45/T151E1 Optical Bore Sight – June 1960

Item Overview

This June 1960 U.S. Army technical manual is the organizational-maintenance repair-parts and special-tools publication for the M45/T151E1 Optical Bore Sight.

The M45 was a portable instrument used to check the alignment of a mortar tube and its sight unit. It helped crews detect errors in elevation and deflection before firing.

This listing is for the technical manual only. It does not include an M45 bore sight, carrying case, mortar sight, special 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 crew aimed the bore sight at a distant reference point and compared its view with the mortar’s regular sight unit. Any difference showed that the sight required adjustment. Proper alignment helped ensure that sight settings matched the actual direction and elevation of the mortar 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. Later M45-series instruments supported several generations of U.S. mortar equipment, including 81mm and 120mm systems.

Published in June 1960, this manual documents the original parts-support system for a Cold War optical instrument that remained useful for decades.

Manual Contents

TM 9-1240-278-20P helped maintenance personnel identify authorized parts 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
• Exploded assembly illustrations
• Part-number and stock-number references
• 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 components.

Identification

• Manual number: TM 9-1240-278-20P
• Publication date: June 1960
• Covered equipment: M45/T151E1 Optical Bore Sight
• 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
• Related manual: TM 9-1240-278-12, December 1959

Collector and Research Value

This manual is a valuable reference for identifying early M45 bore-sight components. It also documents how Army units supported and maintained mortar-alignment equipment during the early Cold War.

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 .1", Approx weight .2lbs.

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