The barrel assembly used with the 60-mm mortar is the M225 cannon (fig. 14-2). It consists of a barrel, fire selector, firing pin, trigger, and range indicator. The lower portion of the barrel is externally threaded. The external threads provide extra cooling surface and also help to strengthened the barrel. The baseplug ends in a spherical projection that is flattened on two sides. The spherical projection fits into the locking cap of the M7 and M8 baseplates. The M224 has two firing modes: conventional and hand-held. Each mode requires different equipment and procedures.

CONVENTIONAL MODE

The BIPOD ASSEMBLY (fig. 14-3) consists of three major assemblies: the leg assembly, the elevating mechanism assembly, and the traversing mechanism assembly.

The BASEPLATE ASSEMBLY (fig. 14-4) is of one-piece construction and it supports and aligns the mortar for firing. The baseplate contains a rotating socket that holds the spherical projection of the barrel. The socket retaining ring holds the rotating socket in place. The open end of the socket MUST ALWAYS point in the direction of fire. The bottom of the baseplate has reinforced ribs that hold the baseplate in position after being seated in the ground.

In the conventional mode, the M7 baseplate, the sight unit (M64/M64Al), and the biped are used. The

Figure 14-3.--Bipod assembly (M170).

Figure 14-4.-Baseplate (M7 and M8).

principle of this weapon is similar to the 81-mm mortar or any other mortar.