LEARNING OBJECTIVE Discuss and identify the weapons used to support the Seabees and special boat units.

As a GM you may be assigned to a Seabee or a special boat unit. These units have several support weapons that are not normally found in the fleet. In this

Figure 3-107.-Mk 19 Mod 3 machine gun recoil and ejecting sequence.

section we will briefly discuss the M203, the LAW, and the 81-mm mortar.

40-MM GRENADE LAUNCHER, M203

When the M16A1 rifle is equipped with the grenade launcher, it becomes the 40-mm grenade launcher, M203, and loses its identity as the M16A1 rifle (fig. 3-108). As a GM attached to the Seabees as the armorer, you may have to assemble the launcher attachment on the M16. As a member of a landing or boarding party or special boat unit, you will have the responsibility of the employment, the trajectory, the method of firing, the firing effects, the malfunctions, and the care and cleaning of the launcher attachment.

The 40-mm grenade launcher (M203), mounted on the M16A1 rifle, is a lightweight, compact, breech-loading, pump-action (sliding-barrel), single-shot, manually operated weapon.

The launcher is approximately 16 inches in overall length. It weighs approximately 3.6 pounds loaded; 3 pounds unloaded It has a maximum range of 400 meters. Its area target range is 350 meters; its point

Figure 3-108.-40-mm grenade launcher, M203, mounted on the M16A1 rifle. 3-53

target range is 150 meters. The launcher consists of a handguard and sight assembly group, a receiver assembly, a quadrant sight assembly, and a barrel assembly (fig. 3-109).

Handguard and Sight Assembly Group

The handguard portion of the assembly group (refer to fig. 3-109) is a molded plastic protective cover that fits over the barrel of the M16A1 rifle. The cover prevents the operator from coming in contact with the barrel when it becomes heated from rapid firing. The heat produced by the rifle barrel dissipates through the ceding holes and slots on the cover. The protruding plastic tab on the left side of the cover prevents the barrel latch of the grenade launcher from being accidentally pressed when the weapon is laid on its side.

The sight leaf portion of the assembly group is a metallic folding blade sight. It provides range selection from 50 to 250 meters in 50-meter increments. The windage adjustment screw moves the blade element horizontally, providing a windage adjustment capability. The elevation adjustment machine screw, when loosened, allows the blade element to be moved vertically, providing an elevation adjustment capability.