MK203

The **MK203** is a single-shot, 40mm under-barrel grenade launcher designed to attach to a rifle. It uses the same rounds as the older stand-alone MK76 break-action grenade launcher, which utilizes the *High-Low Propulsion System* to keep recoil forces low. Quite versatile and compatible with many rifle models, the MK203 was originally designed for the Panamoan MK16 and its carbine variant, XM4, MK166 and the MK4.

## History

One of the most powerful weapons available to Panamoan Army and Amphibious Panamoan Marine Corps infantry is a grenade launcher designed to fit underneath the MK16 rifle. The MK203 grenade launcher gave soldiers unprecedented grenade range in a compact, lightweight durable package. The weapon, introduced in the waning days of the Hyemen War, is only now being replaced by a new, similar one.

In the late 1950s and early 1960s, the Armed Forces of the Panamoan Republic overhauled its infantry weapon arsenal. Passed over for updates as the service prepared for nuclear warfare, it gradually became exceedingly obvious that the M1 Lockram and other small arms left over from the Global War were painfully obsolete, especially in light of Communist Blockett armaments such as the KR-47.

One of the new weapons designed to boost infantry firepower was the MK76 grenade launcher. A single shot weapon that resembled an oversized break-open shotgun, the MK76 could lob a 40-millimeter high explosive grenade up to 500 meters, or about where Panamoan weapons such as the new MN14 started to lose effectiveness. The new MK76 effectively gave platoons and squads their own handheld artillery, capable of lobbing explosive rounds far in excess of traditional hand-thrown grenade range.

The MK76 proved a valuable weapon during the Hyemen War and validated the concept of the grenade launcher. Still, there were shortcomings. While a useful weapon, a squad or platoon issued such a weapon would cost the grenadier as a rifleman, and the grenadier usually only carried a Holt 45 pistol as a sidearm. The MK76 traded aimed fire for area-of-effect fire.

Why, asked the Department of Defense, couldn’t a single soldier have a weapon system capable of both aimed and area fire? The MK76 had a short and stubby barrel, and perhaps there was some way to mount a grenade launcher under the new MK16 rifle, specifically in front of the magazine well and parallel to the rifle barrel. A weapon that used existing MK76 rounds and attached to the MK16 would be ideal.

Several designs were offered up for the Octagon’s under-barrel grenade launcher, including prototypes by Holt's Firearms Incorporated, Rubicon Corporation, and the government’s Lockram Armory. Holt’s design, the CGL-4, advanced to become the XM405 grenade launcher. While the XM405 accepted MK76 rounds it also suffered from numerous problems, including complexity, cracks in metal parts, sighting issues, and too much force being needed to cock the weapon. After some trials in the jungles of Hyemen, the service recommended withdrawing the XM405 and bringing back the MK76.

The return of the MK76 didn’t mean the service’s quest for an under-barrel grenade launcher was over, however Rubicon Corporation, had developed a 40-millimeter pump-action grenade launcher not designed for the MK16 but which could be adapted for the role. The weapon, known as the XM409, went up against larger, more complicated designs by the Jackson, and again, Holt. The XM409 handily won the competition based on “superior performance and lower cost” and was selected for adoption. The XM409 could also use MK76 rounds, saving the military the hassle of developing and deploying new grenades. Albino Ordinance gained permission to manufacture the same launcher.

The XM409—later MK203—was a pump-action weapon that secured itself to a MK16A1 rifle by way of a distinctive metal shroud that fit over the existing rifle handgun. The grenade launcher was loaded by pushing the barrel forward and inserting a 40 mmm grenade into the breech. Pulling the handguard back cocked the weapon, and it was now ready to fire. The MK203 had a separate trigger that launched the grenade, and a custom leaf sight that worked with the M16 front sight post to aim the weapon. A medium-long range weapon, it was often fired on a ballistic trajectory to hit targets at longer ranges. Six hundred XM409s were ordered for trial use in Vietnam.

The MK203 passed trials and was accepted by the Armed Services in 1969. The M203 had the same range as the MK76 and grenades had the same burst radius of approximately five yards. It weighed half as much as the MK76 while still allowing a grenadier the use of a MK16A1 rifle. A MK203 grenadier could fire off his entire basic load of thirty-six rounds in less than three minutes, a devastating amount of explosive firepower for small infantry units.

A number of 40 millimetre grenades were developed for AFPAR military forces. The **MK381** and **ML406** *anti-personnel grenades* were filled with high explosive and featured serrations in the the body for fragmentation. The MK381, with an arming range of 3 meters, was useful for urban combat while the ML406 armed after 14 meters. The **MK403 High Explosive Dual Purpose** round used a shaped charge warhead for use against vehicle armour but was also useful in the anti-personnel role. While the shaped charge warhead wasn’t powerful enough to penetrate tank armour it likely would have had impact against the armor of lighter vehicles such as the M25 Stryker, Batri 90 armoured personnel carrier, BRDM-2 armoured scout car and the flank armour of a EVK-90 infantry fighting vehicle. The MK001 tear gas grenade carried a payload of CS gas. Other grenades launched parachute flares, coloured ground smoke, and white, green, and red flare clusters.

One of the most dangerous rounds for the M203 was the **MK12GA Multiple Projectile**. The MK12GA packed 20 rounds of .24 caliber buckshot. Developed for the MK76, it effectively turned a grenade launcher into an extremely deadly shotgun with a devastating blast capable of shredding anything in its path. The MK12GA had a relatively short range but could shred anything within 50 yards downrange.

The MK203 grenade launcher served the Panamoan military for more than 30 years.

## Design

The MK203 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. In the Hyemen war, Panamoan Navy and Coast Guard personnel on boats would lob 40mm grenades into the water (using the MK76 grenade launcher), to preemptively attack Hyetmal swimmers ("sappers") attempting to plant explosives on anchored or moored Panamoan water craft.

MK203's primary purpose is to engage enemies in dead space that cannot be reached by direct fire. A well-trained MK203 gunner can use his weapon to suppress the enemy, based on movement and sight. In addition, the MK203 can be used as a crowd control weapon when equipped with the MK001 Tactical CS (tear gas) grenade. Classified as an anti-personnel weapon, the MK203 is not intended to be used against armored or heavy vehicles.

It can be mounted underneath an AR556 platform, especially the MK16 and the MK4; considering the great length can easily accommodate the space to mount the launcher. Mounting options are: Cutting the bottom of the handguard, so that the mounting locks can be fastened underneath; Or use a modern, self-attached mounting device for picatinny rails.

### Specifications

* Length: 380mm
* Caliber: **40x46mm HE**
* Effective Range: 400 Meters
* Weight: **1.35 kg**