Bearing Housing Assembly (7). The bearing housing assembly houses the bearings which permit the
smooth, compensating motion when the weapon is elevated. The stem holds the optical instrument
support, which seats the M137/M137A2/M137A3 telescope. It also provides the bearing in which the
M171A1 mount is cross and elevation leveled. Located at the base of the stem are the cross level vial
and elevation level vial.
Battery Enclosure Assembly (8). The battery enclosure is located on the optical instrument rocker
assembly. It is used to hold the battery.
M172/M172A1 Telescope and Quadrant Mount
M 1 7 2 /M 1 7 2 A 1
1 fc 0 1 2
Telescope Mounting Bracket (1). The telescope mounting bracket, attached to the top portion of the
adapter assembly, supports the M138/M138A1 telescope. Seats are included to support a M1A2
gunner's quadrant when fine elevation settings are required.
Access Cover (2). The access cover is located on top of the housing on the quadrant support assembly.
The purpose of the access cover is to protect and aid in alignment of the worm wheel gear sector.
Adapter Assembly (3). The adapter assembly supports the M18/M18A1 quadrant. This assembly
pivots about an axis, parallel to the weapon bore, to facilitate cross leveling.
Quadrant Support Assembly (4). The support assembly provides the keyed interface for assembling the
M172/M172A1 mount to the weapon mounting adapter. It also includes the cross-leveling mechanism
for the M172/M172A1 mount.
Worm Shaft Assembly (5). The worm shaft assembly is located in the housing on the support assembly
and is operated using the cross level knob. The worm shaft assembly is used to actuate the adapter