User:Patton123/M203

Development
The U.S. Army and Marine Corps began issuing the M79 grenade launcher in 1959. The M79 was a single-shot, break-open weapon that fired 40x46 mm grenades and strongly resembled a sawn-off shotgun. It was used to give small units long-range indirect fire capabilities when mortars were unavailable or unsuitable, a task it performed well. It was well liked among troops of all services for its accuracy, light weight and firepower. In spite of this popularity, the M79 had some serious drawbacks. Its break-open nature nature greatly reduced rate of fire and made it difficult to correct aim when firing in strong winds or other difficult conditions. It also prevented the gunner from carrying another weapon in case the enemy drew close, leaving him dependent on his squad for protection.

In 1962, the Army's Special Purpose Individual Weapon program (SPIW) developed plans for a radical new weapon that could fire both flechettes (steel darts) and 40 mm grenades. Acording to the official document, the intent of the SPIW was "to provide the individual soldier with a weapon system possesing the capability to engage point and area targets to a range of 400 meters". The plan was critised as being far too advanced for its time, and failed to develop a successful weapon system. The idea of combining a 40 mm grenade launcher with a rifle, however, would endure. In June 1964, Colt unveiled a 40 mm grenade launcher designated the CGL-4 that mounted underneath the barrel of the M16 rifle. It was quickly adopted as the XM148 by the U.S. Army on an experimental basis, seeing service with a few selected units. The grenade launcher was praised for its great firepower, though it prooved to be too fragile to last long in a combat environment.

Spurred on by the success of the XM148, the Grenade Launcher Attachment Development program was instituted in 1967 to develop an improved 40 mm grenade launcher. Of the 17 companies solicited, only three submitted designs for evaluation. By far the most successful of these weapons during testing was a pump-action grenade launcher developed by the AAI Corporation. The AAI Coporation, which had previously taken part in the SPIW program, created a simple, aluminium-barrelled, single-shot grenade launcher. It was accepted by the Army for field trials and designated the XM203.

The new weapon entered service as the M203 grenade launcher in 1970. Production was soon switched to Colt, who, unlike AAI, had facilities to mass produce the weapon.

Design details
The M203 is a single-shot, breach loaded grenade launcher designed for attachment to the U.S. M16 rifle and M4 carbine, though it can also be attached to other weapons. It fires 40x46 mm grenades, usually high explosive, though a number of other grenades, such as smoke, flare and CS gas, are available.

The grenade launcher barrel is 305 mm long and has a six-groove rifling twist rate of one turn in 1220 mm.

The M203's action is very similar to a rifle, though much simpler. It has a spring-loaded firing pin that strikes the primer of the cartidge when the trigger is pressed. The spent cartridge is expelled by a spring-loaded ejector when the barrel is opened by releasing a catch and shoving it forward, ready for a new grenade to be inserted. The M203 has two available sights: the quadrant sight and the leaf sight or "battlesight". The quadrant sight is an adjustable sight that fixes to the carrying handle of the rifle and facilitates very precise firing of the launcher, but takes time to operate. The leaf sight, or "battlesight", is an open ladder sight fixed to the rifle's handguard that allows very quick aiming, albeit with a lower degree of accuracy.

Tactically, the M203 is used for clearing caves, bunkers and buildings, covering "dead space" (Areas which cannot be fired directly because of obstructions such as trees, rocks and hills) and to eleminate groups of enemy soldiers between the ranges of hand grenades and artillery. It is also used to fire smoke and flares to conceal and detect movement respectively. The high-explosive dual-purpose round is also able to penetrate up to 50 mm of steel, and thus is effective against lightly armoured vehicles.