The handguard portion of the assembly group is a molded plastic protective cover that fits over the barrel of the Ml6A1 rifle. The cover prevents the operator from coming into contact with the barrel when it becomes heated from rapid firing. The heat produced by the rifle barrel dissipates through the cooling holes and slots in 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

Figure 13-1.-The 40-mm grenade launcher, M203, mounted on the M16Al rifle.

Figure 3-3.-Quadrant sight assembly.

from 50 to 250 meters in 50-meter increments. The windage adjustment screw moves the blade element horizontally to provide windage adjustment capabilities. The elevation adjustment machine screw, when loosened, allows the blade element to be moved vertically, providing elevation adjustment capabilities. The M203 also has a quadrant sight assembly (fig. 13-3) that connects to the carrying handle of the M16 rifle. It consists of a sight arm, a range selection quadrant, an aperture, and post for sighting operation of the launcher. The range selection quadrant has embossed range graduations from 50 to 400 in 25-meter increments. The 25-meter increments also allow for better accuracy at a greater number of range variations than the quadrant sight (fig. 13-4). For elevation adjustment, turn the front sight post to the right to decrease elevation and to the left to increase elevation.

NOTE

On elevation, one notch equals 5 meters at 200 meters. For windage adjustment, press the rear sight retainer and move the aperture away from the barrel to move

the trajectory of the projectile to the left. Move the aperture toward the barrel to move the trajectory to the right.

NOTE

On windage adjustment, one notch equals

1.5 meters at 200 meters.

BARREL ASSEMBLY

The barrel of the barrel assembly is constructed of specially treated and machined aluminum. The barrel extension is a rectangular, chrome-plated steel bar. It attaches to the barrel and provides a means of attaching the barrel to the receiver assembly. The handgrip is a molded plastic corrugated sleeve. When the grenade launcher is being fired, the plastic handgrip allows the operator to hold the launcher without discomfort from the heat.