Technical Manual (TM 9-1240-277-35P) for XM42 Periscope December 1963

Technical Manual (TM 9-1240-277-35P) for XM42 Periscope December 1963

Technical Manual (TM 9-1240-277-35P) for XM42 Periscope – December 1963

Item Overview

This December 1963 U.S. Army technical manual is the repair-parts and special-tools publication for the XM42 Tank Periscope.

The XM42 was the experimental designation for the optical instrument later standardized as the M42 Tank Periscope. It formed part of the direct-fire sighting system used on the M109 155mm Self-Propelled Howitzer.

This listing is for the technical manual only. It does not include an XM42 or M42 periscope, elbow telescope, telescope mount, tools, or replacement parts.

Purpose of the XM42 Periscope

The XM42 was a unity-power armored periscope designed for use with the M118C Elbow Telescope. Together, these instruments provided the gun crew with a direct-fire optical line of sight.

The periscope shifted the telescope’s viewing path around the howitzer’s gun and muzzle-brake area. This allowed the protected telescope inside the vehicle to see forward while aiming at visible targets.

The XM42 was part of the weapon’s fire-control equipment. It was not a general observation periscope for the driver or commander.

Historical Background

The XM42 was developed during the creation of the M109 self-propelled howitzer. The M109 was standardized in 1963 and became one of the U.S. Army’s most important tracked artillery systems.

Published in December 1963, this manual comes from the beginning of the M109’s service life. Its use of the experimental “XM” designation records the transition between development equipment and the standardized M42 periscope.

The standardized M42 was identified by part number 7645543 and FSN 1240-864-2933, later written as NSN 1240-00-864-2933. It continued serving with the M109 family as part of its direct-fire optical system.

Manual Contents

TM 9-1240-277-35P helped maintenance personnel identify authorized parts and equipment. Its contents include:

• Major periscope assemblies
• Optical and mechanical components
• Window, prism, and housing parts
• Seals, retainers, and 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 XM42 and early M42 components.

Identification

• Manual number: TM 9-1240-277-35P
• Publication date: December 1963
• Covered equipment: XM42 Tank Periscope
• Later standardized designation: M42 Tank Periscope
• Manual type: Repair parts and special tools list
• Equipment type: Armored artillery fire-control periscope
• Associated telescope: M118C Elbow Telescope
• End-item application: M109 155mm Self-Propelled Howitzer

Collector and Research Value

This manual documents the XM42 during its transition into the standardized M42. It is a valuable reference for early M109 restoration projects, military-optics research, and Cold War artillery collections.

Ideal For

• XM42 and M42 parts identification
• M109 howitzer restoration projects
• Military-optics collections
• U.S. Army artillery displays
• Museum and educational exhibits
• Cold War technical-library collections

Approx length 8", Approx width 10", Approx height .15", Approx weight .2lbs.

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