M203 40mm Grenade Launcher
The M203A2 grenade launcher provides a mounting system compatible with the M16A4 rifle and M4 carbine. The modification to the previous M203 and M203A1 designs includes a quick-attach bracket for the grenade launcher and a leaf sight to attach to the MIL-STD-1913 Rail Adapter System. The weapon increases the lethality and operational flexibility of the soldier with a grenade capability that bridges the gap between hand grenade and mortar.
The earlier M203 was used while attached to the M16A1 and M16A2 5.56mm rifles, and could be used with the XM177E2 submachine gun and other shortened variants of the M16 rifle family. The base M203 is a lightweight, compact, breech loading, pump action, single shot launcher. The launcher consists of a hand guard and sight assembly with an adjustable metallic folding, short-range blade sight assembly, and an aluminum receiver assembly which houses the barrel latch, barrel stop and firing mechanism. The launcher is capable of firing a variety of low velocity 40mm ammunition. The launcher also has a quadrant sight which may be attached to the host rifle's carrying handle and is used when precision is required out to the maximum effective range of the weapon. The M203A1 has a shorter barrel and a quick release mechanism to facilitate rapidly attaching and detaching the weapon. The M203A1 was primarily intended for use on the M4 carbine and similar short barrel members of the M16 family.
The M203 series could also be fitted with a Day-Night Sight (DNS) that provides an aiming device for the M203 Grenade Launcher for all lighting conditions, increasing the lethality and operational flexibility of the soldier. The DNS provides increased accuracy over the current quadrant and leaf sight systems for both point and area targets. The DNS is equipped with integral iron sights in case of electronics failure or for situational expediency.
The standard leaf sight is a folding, adjustable open ladder design that permits rapid firing with out manipulation. The leaf sight uses the front sight post of the M16 rifle or M4 carbine as the front aiming post. The leaf sight base is permanently attached to the rifle hand guard by two mounting screws. The leaf sight base serves to protect the leaf sight from damage when the leaf is not being used and is in the down position. The leaf sight mount is attached to the sight base and is used to rise and lower the sight leaf blade. The leaf sight is graduated in 50-meter increments from 50 to 250 meters.
The quadrant sight assembly mounts on the left side of the carrying handle of the M16 rifle. The quadrant sight arm serves a dual purpose. It mounts the sight aperture arm (which holds the sight aperture) and the sight post arm (which holds the front sight post). The following procedure is used to fire with the quadrant sight. The front sight post can be used to make minor adjustments in elevation when zeroing the launcher. For elevation adjustments, turn the adjustment screw on the sight post clockwise to decrease elevation and counterclockwise to increase elevation. One full turn on the adjustment screw will move the impact of the projectile 5 meters at a range of 200 meters. The rear sight aperture can be adjusted for minor changes in deflection when zeroing the launcher. For windage adjustment, press the rear sight retainer and move the aperture away from the barrel to move the impact to the left. One notch on the rear aperture will move the impact of the projectile 1 and 1/2 meters at a range of 200 meters.
The standard 40x46mm high explosive grenade has an effective casualty radius of 5 meters. The effective casualty radius is defined as the radius of a circle about the point of detonation in which it may be expected that 50 percent of exposed troops will become casualties. Safe-weapon practices for firing the M203 grenade launcher require a minimum safe distance of 130 meters for high explosive rounds, and 165 meters for HEDP. Range regulations stipulate that all targets have to be more than 200 meters away. The danger radius of the high explosive grenades is 130 meters (427 feet). The M386, M397, M397A1, M406, and M433 rounds arm within 14 to 27 meters (46 to 89 feet). The M361 and M441 rounds arm within 2.4 to 3 meters (8 to 10 feet).
The Marine fire team leader/grenadier employed the grenade launcher in the offense to destroy groups of enemy personnel and to provide close fire support in the assault in conjunction with, and to supplement, other supporting fires. The fire team leader/grenadier personally selected targets and delivered the fire of the grenade launcher during the attack. In the last 35 meters of the assault, when the fires of the grenade launcher might endanger friendly assaulting troops on the objective, the fire team leader/grenadier employed the multi-projectile anti-personnel round. The multi-projectile round could be fired from the assault skirmish line without endangering the other assaulting Marines. The fire team leader/grenadier could fire high explosive rounds at targets that were far enough away so that the exploding high explosive round would not endanger the assaulting squad. High explosive rounds required an arming distance of approximately 30 meters.
During the assault, the fire team leader/grenadier might employ his rifle until suitable targets appeared or until he had time to reload the M203. Suitable M203 targets were enemy automatic rifle positions, machine gun positions, and other crew served weapons within the fire team sector. This method of employment was used when a heavy volume of fire was needed.
The M203 could engage a window sized target out to 150 meters and an area type target out to 450 meters. The soldier was trained to apply the marksmanship principles: steady position, aiming, breath control, and trigger squeeze. The soldier wold fire training practice rounds and one high explosive round for familiarization. The soldier would be trained to correctly zero the sights, correct a malfunction, and perform maintenance on the M203.
In the defense, the fire team leader/grenadier's firing position would enable him to control his fire team and deliver grenade launcher fires over the entire fire team sector of fire. Primary and supplementary positions were prepared, which provided maximum cover and concealment consistent with the assigned mission. Extreme care had to be taken to ensure that fields of fire were cleared of obstructions, which might cause premature detonation of the projectile. As the enemy approached the defensive position, he would be subjected to an ever increasing volume of fire. Initially, the fire team leader/grenadier would use the rifle portion of the weapon. As the enemy got nearer to friendly positions, he would use the grenade launcher. He would fire on enemy automatic weapons and enemy troops who were in defilade. This would silence an enemy base of fire and cause enemy troops to leave covered positions so the automatic riflemen could engage them.
One final critical factor in selection of non-lethal systems was the need to be able to deliver the munitions using the organic weapon systems in the Marine rifle company's table of equipment. Learning new delivery systems would require additional training time and increase the combat load of the individual Marine. The decision was to require that new material could be fired from the M203, a combination of grenade launcher and rifle, and the standard 12-gauge shotgun. The M203 grenade launching system could be adapted to fire 37mm non-lethal munitions procured for Operation United Shield and was the preferred delivery system for these munitions. The M203 in effect included the host the M16 (though the designation applied only to the grenade launcher component) and could provide lethality promptly when required. The infantry's familiarity with the M203 contributed to accuracy in non-lethal systems as well. The 12-gauge shotgun also provides versatility, and could easily be employed as a lethal weapon by quick selection of munitions.
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