Product Overview: M45 Optical Bore Sight W/E
NSN: 1240-00-152-3512
P/N: 10549221

Top row: M102 Carrying Case, M62A1C Telescope
Bottom Row: Body Assembly

Description
General: Bore sight M45 (T151E1) is a fixed-focus telescope adapted used to align the axis of the bore of the 81-mm, 105-mm, and 4.2-inch mortars with a distant aiming point. The bore sight is constructed so that the telescope line-of-sight lies in the plane established by the centerlines of the "V" slides. When the bore sight is properly secured to a mortar tube, the centerline of the contacting "V" slide is parallel to the centerline of the mortar tube. The cross-level vial, when centered, indicates that the centerlines of both slides, the elbow telescope, and the mortar tube lie in the same vertical plane. Therefore, the line-of-sight of the telescope coincides with the azimuth angle of the mortar tube regardless of which "V" slide of the bore sight is contacting the mortar tube. The bore sight is accurate if the aiming point appears on the vertical crossline of the telescope, regardless of which "V" slide of the sight is contacting the mortar tube. A displacement in azimuth beyond the normal construction tolerance of 1 mil indicates either an inaccurate bore sight or a mortar tube which is not clean and smooth. The elevation level vial should be at 45 degrees to both "V" slides. It will level only when both slides (upon installation on the mortar tube) are at an angle of 45 degrees (800 mils) to the horizontal plane.

Basic Components: The bore sight M45 (T151E1) consists of the elbow telescope M62A1C, body assembly, telescope clamp, two strap assemblies, and a clamp assembly.

1. Elbow Telescope M62A1C: The elbow telescope M62A1C is used to establish a definite line-of-sight for the 81-mm, 105-mm, and 4.2-inch mortars. For a complete description of the telescope's features, refer to TM-9-1604.

2. Body Assembly: The body assembly incorporates two perpendicular "V" slides which house the cross level vial, a pivot shaft, strap shaft, and hooks. The level vials are used to determine the angle of elevation and to prove the integrity and perpendicularity of the "V" slides.

a. Pivot shaft: The pivot shaft is a slip fit through the bore sight mounting clevis and a drive fit in the telescope clamp. This shaft is the pivot around which the telescope swings.
Note: A cap screw in the body clears a radical pivot slot in the telescope clamp for normal travel, but engages the end of the slot to prevent damage to the telescope which might be caused if the telescope should contact the body.

b. Strap Shaft: The strap shaft slides in to the bore sight body and is retained with an external snap ring. The shaft has an eye head to which the strap snap attaches.

c. Hooks: The hooks are attached to the underside of the "V" slides with four screws. The hooks hold the strap loops secure.

3. Telescope clamp: The telescope clamp maintains that line of sight established by the elbow telescope in the plane described for the mortar tube by the centerline of the "V" slides. The telescope clamp is a slotted tube cylindrical clamp, with a casted externally mounted arm, which is drilled to receive the pivot shaft.

4. Strap Assemblies: Two strap assemblies are supplied with each bore sight. One strap assembly has a snap fastener at one end, while the other strap has a loop at one end. The strap assemblies, with the aid of the clamp assembly, are used to secure the bore sight against the mortar tube.

5. Clamp Assembly: The clamp assembly is used to apply tension to the strap assemblies which secure the bore sight body against the mortar tube. The clamp assembly consists of a bracket fitted with two catches, each of which secures a strap assembly to the clamp assembly; and a clamp screw which when advanced through the bracket applies pressure against the mortar tube through a swiveling shoe at the end of the screw. The resultant force tightens the straps, in turn securing the bore sight against the mortar tube.

Equipment Issued With Bore Sight M45 (T151E1)
Carrying case M102 is the only piece of equipment issued with the bore sight M45 (T151E1). The case is a small metal container in which the bore sight is stored to protect it from damage when it is being shipped or not in use. A metal handle is connected to the cover of the case for easy portability. One catch fastener is provided to secure the lid to the case.