The M203 is a single-shot 40 mm under-barrel grenade launcher designed to attach to a rifle. It uses the same rounds as the older stand-alone M79 break-action grenade launcher, which utilizes the High-Low Propulsion System to keep recoil forces low. Though versatile, and compatible with many rifle models, the M203 was originally designed for the U.S. M16 and its variant, the M4 Carbine. The launcher can also be mounted onto a C7, a Canadian version of the M16 rifle, however, this requires the prior removal of the bottom handguard.
The M203 grenade launcher is intended to be used as close fire support against point and area targets. The round is designed to be effective at breaking through windows and exploding inside, blowing up doors, producing multiple casualties, destroying bunkers or emplacements, and damaging or disabling soft-skinned vehicles.
The M203 Grenade launcher system comes with a variety of components, usually including the launcher, adaptors for attachment to assault rifles, and leaf sights (which can be used with the rifle's front sight post). M203s can also come with quadrant sights, mounting to a MIL-STD 1913 Rail, or to the carrying handle of an M16 rifle.
In the Vietnam war, U.S. Navy and Coast Guard personnel on boats would lob M203 grenades into the water (using the M79 grenade launcher), to preemptively attack Viet Cong swimmers ("sappers") attempting to plant explosives on anchored or moored U.S. water craft. Its primary purpose is to engage enemies in dead space that cannot be reached by direct fire. A well-trained M203 gunner can use his weapon to suppress the enemy, based on movement and sight. In addition, the M203 can be used as a crowd control weapon when equipped with the M651 Tactical CS (tear gas) grenade. Classified as an anti-personnel weapon, the M203 is not intended to be used against armored or heavy vehicles. Visit Wikipedia.