M203 grenade launcher

The M203 is a single shot 40 mm 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 hand-guard.

Stand-alone variants of the M203 exist, as do versions designed specifically for many other rifles. The device attaches under the barrel, the launcher trigger being in the rear of the launcher, just forward of the rifle magazine. The rifle magazine functions as a hand grip when firing the M203. A separate sighting system is added to rifles fitted with the M203, as the rifle's standard sights are not matched to the launcher. The version fitted to the Canadian C7 has a sight attached to the side of the launcher, either on the left or right depending on the user's needs.

Rounds

The M203 is able to fire a variety of different rounds for many purposes. According to the U.S. ARMY FIELD MANUAL FM 3-22.31 40-MM GRENADE LAUNCHER, M203, there are 8 different rounds for the M203:

1. (M433) High-Explosive. Dual Purpose Round. The HEDP round has an olive drab aluminum skirt with a steel cup attached, white markings, and a gold ogive (head of the round). It penetrates at least 5 cm (2 inches) when fired straight at steel armor at 150 meters or less, or, at a point target, it arms between 14 and 27 meters, causes casualties within a 130-meter radius, and has a kill radius of 5 meters.
   
2. (M406) High-Explosive Round. The HE round has an olive drab aluminum skirt with a steel projectile attached, gold markings, and a yellow ogive. It arms between 14 and 27 meters, produces a ground burst that causes casualties within a 130-meter radius, and has a kill radius of 5 meters.
   
3. (M583A1) Star Parachute Round. This round is white impact or bar alloy aluminum, with black markings. It is used for illumination and signals and is lighter and more accurate than comparable handheld signal rounds. The parachute attached to the round deploys upon ejection to lower the candle at 7 feet per second. The candle burns for about 40 seconds. A raised letter on the top of the round denotes the color of the parachute.
   
4. (M585) White Star Cluster Round. This round is white impact or bar aluminum alloy, with black markings. The attached plastic ogive has five raised dots for night identification. The round is used for illumination or signals. It is lighter and more accurate than comparable handheld signal rounds. The individual stars burn for about 7 seconds during free fall.
5. (M713) Ground Marker Round. This round is light green impact aluminum with black markings. It is used for aerial identification and for marking the location of soldiers on the ground. It arms between 15 and 45 meters. If a fuse fails to function on impact, the output mixture provided in the front end of the delay casing backs up the impact feature. The color of the ogive indicates the color of the smoke.
   
6. (M781) Practice Round. Used for practice, this round is blue zinc or aluminum, with white markings. It produces a yellow or orange signature on impact, arms between 14 and 27 meters, and has a danger radius of 20 meters.
   
7. (M651) CS Round. This round is gray aluminum with a green casing and black markings. Though it is a multipurpose round, it is most effective for riot control and in Urban Operations. It arms between 10 and 30 meters and produces a white cloud of CS gas on impact.
   
8. (M576) Buckshot Round. This round is olive drab with black markings. Though it is a multipurpose round, it is most effective in thick vegetated areas or for room clearing. Inside, it has 20 metal pellets, each weighing 24 grains, with a muzzle velocity of 269 meters per second. The round has no mechanical-type fuse.
   

Source

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