M203 40mm underbarrel grenade launcher (USA)

XM148 / Colt CG-4 grenade launcher on early model M16 rifle. The XM148 served as a proof of concept for more sucessful M203 grenade launcher

M203 40mm grenade launcher installed on the M16A1 assault rifle

M203 grenade launcher with M16 handguards, removed from the rifle

Drawing from M203 manual, which depicts the loading process, from top to bottom: 1) opening the breech 2) inserting the round of ammunition and 3) closing the breech

Caliber: 40mm (40x46)
Overall length: 380 mm
Weight: 1.36 kg unloaded
Effective range: up to 150 meters point target, up to 350 meters area target


The M203 grenade launcher has been developed between 1967 and 1968 by the AAI Corporation of USA on the contract from US Army. this contract has been issued on the basis of the experience, gained by the US armed forces in Vietnam with the M79 40mm grenade launcher (which was successful design but required an additional personal defense weapon to be carried by grenadier) and unsuccessful XM-148/CG-4 40mm underbarrel grenade launcher, developed in mid-sixties by Colt in attempt to cure deficiencies of the M79. The new underbarrel grenade launcher was intended to be used with all available 40mm ammunition, and to be attached to the existing infantry rifle then in service, the M16A1.In the late 1968 the AAI design has been type classified as XM203, and in early 1970 first M203 units went to Vietnam for field evaluation. After successful tests US Army ordered large quantities of M203, and since AAI had no resources fore mass production, the manufacturing contract has been issued to Colt. latter on, more or less exact copies of M203 were produced in Egypt, South Korea and Bulgaria (as UBGL-M1, with mount suitable for Kalashnikov AKM and AK-74 type rifles). During the 1990s, M203 went into several modifications, such as shorter-barreled M203A2 (with 9 inch barrel, as opposed to standard 12 inch barrel), intended for shorter M4 carbines used by US SOCOM, as well as versions with MIL-STD 1913 (Picatinny rail) compatible mounts. M203 launchers are still being used by US armed forces, and by many other armies, including those of Australia, Israel, South Korea, Philippines, Turkey and some others.


The M203 is a single-shot, breech-loading weapon with rifled barrel. The loading is achieved by sliding the aluminum barrel forward, then inserting the round of ammunition into the breech and sliding the loaded barrel back into the battery. The barrel is held in-battery by the manually controlled lock, which is disengaged by depressing the barrel catch lever at the left side of the launcher, above the middle of the barrel. The loaded cartridge is held at the breech face by the extractor claws, and remains stationary when barrel is opened forward. Once the barrel clears the fired case or unfired round, it is free to fall down from the breech face, so the next round can me loaded if necessary. The self-cocking firing unit with its own trigger is located at the rear of the M203 receiver, also made from aluminum alloy. The manual safety in the form of the swinging flap is located inside the trigger guard, just ahead of the trigger. The rear part of the barrel is covered with polymer handgrip. The standard M203 easily installs on the M16A1 or M16A2 type rifle, and installation requires about 5 minutes of work and a standard screwdriver for clamping screws. If necessary, M203 can be mounted on a separate shoulder-stock / pistol grip assemblies (available from several companies, such as Colt or Knight's Armament) to be used as a stand-alone weapon. Standard sights for M203 are of ladder type, and graduated from 50 to 250 meters in 50m increments. The optional quadrant sight can be installed on the left side of the M16A1/A2 carrying handle, and it allows aiming at the ranges of up to 400 meters.