Notes: The M-203 was developed during the Vietnam War to replace the M-79 and an earlier experimental underbarrel grenade launcher, the XM-148. The M-203 was accepted for service in 1969, and by 2000, almost 300,000 of them had been produced, with the M-203 being used by over thirty countries worldwide. The M-203 was an AAI design, and they built the first production batches. However, even AAI realized that they could not keep up with the even the huge orders from the US military, let alone other countries, and by January of 1970, the M-203 was a Colt product; AAI themselves only manufactured 600 M-203s.

The M-203 grenade launcher kit consists of a base launcher rail that is attached under the barrel of an M-16 or M-4-series assault rifle, the barrel and trigger mechanism, a quadrant sight that is attached to the carrying handle of the rifle, a secondary folding leaf sight behind the front sight of the rifle, and a new handguard. The assembly is very simple and takes less than 5 minutes to attach to the rifle. Once attached, the M-16 or M-4 may be used normally, except that a bayonet or the RAW rifle grenade cannot be used, and the sling attaches to the front of the weapon slightly differently (the sling swivel is attached to the side of the front sight base). The M-203 uses a slide action to open the breech, sliding forward for loading, with a latch on the left side of the interface rail being depressed by the thumb of the shooter’s non-firing hand (assuming he is left-handed) being depressed to unlock the barrel. The round is inserted into the breech, and the barrel slid back again, where it automatically locks into place for firing. The spent case ejects automatically when the breech is opened again. The M-203 is fired using separate trigger group in front of the magazine well of the rifle to which it is attached; the magazine is used as a sort of pistol grip for the M-203. Inside the trigger guard of the M-203 is a safety that looks like a backwards trigger in front of the actual trigger; pushing it forward makes the M-203 ready to fire. When pulled back, the safety blocks the firing pin as well as not providing enough room to put a finger on the trigger. Construction is primarily of steel, with the special handguard being of one-piece semi-flexible plastic (so that it can be fitted onto the rifle), and a 12-inch aluminum alloy barrel.

The Colt Launcher System is a development of the M-203 into a stand-alone launcher. It is basically the M-203 with a snap-on M-16 or M-4 stock and pistol grip. The stock can be removed completely, leaving only the pistol grip, if a more compact weapon is desired.

The widespread adoption by US forces of the M-4 and M-4A1 carbines led to the development of the M-203A1. The mounting kit of the M-203A1 uses handguards with four-point MIL-STD-1913 rails (borrowed from the SOPMOD kit), assuming the shooter’s carbine does not already have them. The modified M-203A1 (which uses a shorter 9-inch barrel to better fit the M-4’s shorter length) can then be easily attached to lower rail of the handguards. The M-203A1 mounting interface also allows it to be easily attached to almost any weapon that has a MIL-STD-1913 rail under the barrel.

RM Equipment of Miami, Florida also introduced a variant of the M-203, called the M-203PI EGLM (Enhanced Grenade Launcher Module), in 1987. (This should not be confused with Colt’s early experiments with an improved M-203, also called the M-203PI at the time; Colt’s experimental M-203PI will be found on the Best Grenade Launchers That Never Were page, once I can do a bit more research). The M-203PI EGLM is version of the M-203 that is similar to the Colt Launcher System, though it is even more flexible in mounting options and ability to use a variety of accessories. Mounting an M-203PI EGLM usually requires very little of no modifications to the weapon upon which it is mounted, though some will require the replacements of their handguards with specially-designed handguards. The M-203PI EGNM may be mounted on its host weapon in one of three ways.

The Interbar Mounting System (IMC) is a special attachment similar in concept to the original M-203, but far more flexible and adaptable in form. The IMC has the virtue of allowing the M-203PI EGLM to be mounted on virtually any rifle, carbine, short-barreled assault rifle, or submachinegun; even a few tactical semiautomatic shotguns are able to mount the M-203PI EGLM (in what must be an incredible one-two punch!) When attached to a host weapon using the IMC, the grenade launcher is on a rock-steady mount. A slight drawback of the IMC is that adding it to a weapon is that it takes more work to attach it or remove it from its host weapon; many host weapons will require the removal of their original handguards and replacement with special handguards incorporating the IMC. (These handguards do, however, generally give the shooter three MIL-STD-1913 rails to use.)

A second way to mount the M-203PI EGLM is by use of the Snap-On Launcher System (SOLA). The SOLA is a special interbar that can be mounted and removed from the host weapon without any special skills or tools. This allows the M-203PI EGLM to be removed or mounted on many most weapons as necessary, with no modifications to the host weapon required. The disadvantage of the SOLA is less flexibility when choosing the host weapon to which it is mounted; in general, it will take a rifle somewhere in length between a Colt Commando and a standard M-16-series weapon.

The M-203PI EGLM can also be attached to a gripstock, Tactical Mounting System (TMS). This gripstock uses an M-4-type collapsible stock that also folds to right to allow the M-203PI EGLM to be used as a "grenade pistol." The gripstock is equipped with a MIL-STD-1913 rail above the interbar, and a foregrip can also be attached to the barrel of the grenade launcher to improve grip and allow for faster actuating of the barrel when loading and unloading (including a foregrip with an adapter for a tactical flashlight).

Construction of the M-203PI EGLM’s grenade launcher module and most of its associated hardware are of aluminum stock; some other parts of the interbar and TMS may be made from steel or polymer as required. At least 28 countries are using the M-203PI EGLM as of late April 2008, including the US. Weight and barrel lengths for the M-203PI EGLM are approximate; I have yet to find any hard information on the proper figures. (If a reader knows, please let me know.)

Twilight 2000 Notes: The M-203A1 was a rare weapon in the Twilight 2000 timeline, even in US special operations units. Outside of US hands, the M-203A1 is virtually unknown (at least, as an issue weapon). The M-203PI EGLM does not exist in the Twilight 2000 timeline.

Notes: This is a magazine-fed pump-action weapon, able to mount a variety of optical and laser sights without damaging the sights. The weapon fires the 40mm NATO High-Velocity rounds of the Mk-19 automatic grenade launcher. It was designed by China Lake for the US Navy SEALs, but is still listed as an experimental weapon, and whether or not it has been combat tested is unknown.

Twilight 2000 Notes: This experimental magazine-fed grenade launcher was issued in small numbers to US Navy SEALs during the Twilight War.

Merc 2000 Notes: This weapon fell prey to budget cuts in the late 1990s.

M-79

Notes: A single-shot grenade launcher introduced by the US during the Vietnam War. The M79 is still in use worldwide. Although replaced in many countries by newer grenade launchers, the M79 is still favored by troops who like its natural pointing qualities. The M79 (known as the thumper, blooper, thump gun, bloop tube, etc.) uses the same grenades as the M203 and loads by breaking open the weapon like a shotgun.

Notes: The original Manville Gun was designed by Charles Manville in 1935. It was essentially a huge, rotary-cylinder 12-gauge shotgun, with a 24-round capacity contained within a large rotary-cylinder which was wind-up and spring-driven. Construction was largely of high-strength aluminum (except for a plastic pistol grip, fore-grip, and some other parts which were made from steel, especially the 11.1-inch barrel), and as might be thought, was large and beastly-heavy. It has no stock, but was equipped with a fore-grip for control. Loading was done by releasing two large-headed finger-tight screws at the of the barrel, which allowed the two halves of the Manville gun to be separated; after loading, the reverse procedure was done. The cylinder was spring-loaded and had to be wound (but in a backward direction from normal). This gave the Manville gun a light trigger pull, but also (in game terms) adds two phases to the reloading time. Each chamber of the cylinder was a complete unit, with its own firing pin. This original 12-gauge Manville Gun had some sales (some would say a surprising amount), but production had stopped by the late 1940s.

In 1936, Manville also came up with a 25mm version of the Manville Gun; this version was nearly identical to the 12-gauge weapon, but used a somewhat simplified weapon and the cylinder held 18 rounds instead of the 24 of the 12-gauge Manville gun. Early models of the 25mm Manville Gun used a 9.75-inch barrel, while later versions used a 9.5-inch barrel and were somewhat lighter than the early models. The later version was much improved in the areas of structural strength and reliability, as well as having more ergonomic pistols grips and foregrips. Both versions could have inserts put in the barrels and cylinders to allow the use of 12 gauge and .38 Special ammunition (though these ammunition types could not be mixed, since they involved a barrel insert as well as cylinder inserts. (The late-model 25mm Manville Gun was used in the movie Dogs of War, called the XM-18 in the movie, though the effects seen in the movie were far greater than an actual 25mm Manville Gun was capable of producing.)

Late in the 1930s, Manville created a version of the Manville Gun which could fire the newly-available 37mm grenades. This version had a 12-round capacity and the mechanism was effectively upside-down with the barrel at the bottom of the cylinder. The 37mm Manville gun was intended to be fired like a repeating mortar under normal circumstances, though it could be fired by one man if he were strong enough to manage the enormous weight. It could also be mounted on the tripods and pintle mounts of the time. Construction was otherwise the same as the late version of the 25mm Manville gun, but there were no barrel and cylinder inserts.

The military and police showed little interest in any version of the Manville Guns, but the Manville Company survived World War 2 by building antiaircraft guns, gun parts for existing large-caliber guns, and – believe it or not – dishwashers! In 1943, Manville gave up on the Manville guns, ordering the destruction of the production machinery, dies, and most of his notes.

Ironically, Dogs of War created a new interest in the Manville Gun in the late 1970s. Frankford Arsenal decided to renew the production of the 37mm Manville gun using new production methods and materials, calling it the MM-1. Later, Frankford made 12-gauge, 25mm, and 40mm versions of the MM-1. These "new" versions of the Manville Gun are far lighter than the originals. Unfortunately, the MM-1 also enjoyed few sales, and though Frankford Arsenal will still make them upon request, they are no longer mass-produced.

Twilight 2000 Notes: Ironically, the Twilight War renewed interest in the Manville Gun and MM-1, particularly in the 25mm and 40mm versions, and Frankford Arsenal was asked by the Pentagon to greatly step production of the MM-1, particularly in those two calibers.

Notes: This Vietnam-era weapon was sort of an oddity to the modern era – it is a hand-cranked belt-fed grenade launcher. It used a very simple method of operation with few moving parts and simple maintenance. The ammunition belt was a custom-made Mylar-backed Dacron belt (earlier fiberglass-reinforced tape belts gave too many problems, and they were quickly replaced). Even the Mylar/Dacron belts were a weak point, good for only about five trips through the Mark 18 before they no longer held the rounds firmly enough, and they too were replaced by cloth belts. The Mark 18 was produced between 1965 and 1968, and used primarily on small boats or in fixed positions such as bunkers; their primary users were the so-called "River Rats" and the SEALs. They could be mounted on M-2HB, M-60, or M-1919 tripods or pintle mounts, but could not be fired without such a mount.

The unusual method of operation of this weapon means that unusual rate of fire rules must be used. The rate of fire for the Mark 18 Mod 0 in sustained fire operations is one-third the Strength rating of the operator; this may be quickened to one-half the Strength rating of the firer for 20 minutes, or 3/4 the Strength rating of the firer for 20 minutes. Firing at a normal rate does not count as fatigue, but firing at a rate of fire 1/2 the firer’s strength counts as one level of fatigue, and firing at 3/4 of the firer’s strength counts as two levels of fatigue. Willpower skill may affect this. Recoil for "automatic" bursts is equal to 1.5 times the amount of rounds which are fired.

Some 1200 of these launchers were produced; however, it was never considered as more than a stopgap weapon, to be used until a "real" automatic grenade launcher could be designed and the bugs worked out. Forerunners of the Mk 19 (below) were already being developed.

Notes: This automatic grenade launcher (often known as the "autoblooper" to troops) was the first practical launcher of its type to be fielded by military force. The original model, the Mark 19 Mod 0, was designed for use by US Navy patrol boats and SEALs in Vietnam. It was a spectacular success, well liked by its troops, but mechanically complex and difficult to care for. A product improvement program began, and the Mod 0 guns were converted to the new Mod 1 specification by 1971, along with new manufacture guns. The Mod 2 was the first serious attempt to streamline the mechanism of the Mark 19 itself; this was unsuccessful, but the Mod 3 variant was, having 47% fewer parts and being strippable without special tools. By 2000, over 21,000 Mark 19s had been built for US forces, with many more being made for 22 other countries.

Notes: The Mark 20 was designed by the Naval Ordnance Station in Louisville, Kentucky to address the biggest problem with the Mark 18 crank-operated grenade launcher – the crank-operation. The Mark 20 was perhaps the first grenade machinegun, and is a selective fire weapon with the low rate of automatic fire which became characteristic of most automatic grenade launchers in the future. Prototypes were available by 1967, and the weapon received its military designation and began combat use in 1968. The Mark 20 uses a rather peculiar method of operation – blow-forward combined with recoil operation. When the Mark 20 is cocked, the barrel is actually pushed forward; the barrel snaps back around the 40mm round when the trigger in the spade grips is pushed. The force of the grenade moving down the barrel moves the barrel forward again, which causes the weapon to be recocked. The bolt, on the other hand, flies back from the recoil and completes the cycle. Though this method of operation means that the weapon has little felt recoil, it is also a very complicated method of operation. The Mark 20 is designed to be fired from pintle or tripod (NLT or NHT) mounts, but it can actually be fired handheld in short bursts. (The designers had intentions to develop the Mark 20 into a version with a standard stock, trigger, and bipod, but this was never done.) The Mark 20 is fed by disintegrating-link belts. Some 1080 of these weapons were built by 1971, when production ended, replaced by the then-new Mark 19 Mod 0 (see above).

Notes: Produced by Milkor USA (a subsidiary or South Africa’s Milkor Defence), the M-32 is a modified form of the Milkor MGL Mark 1 (more commonly known as the MGL-40 or MGL-140). So far, the M-32 is used only by US Marines, though reportedly other branches of the US military, as well as a few other countries, are evaluating or considering buying the M-32. The Marines were combat-testing the M-32 since 2004, with official adoption taking place in 2005.

As with the MGL Mark 1, the M-32 uses a single barrel, fed by a 6-round revolving cylinder. The rear part of the M-32, consisting of most of the gripstock and the rear plate of the cylinders, swings away from the rest of the M-32 for loading. The spring-loaded cylinders are wound with a knob at the front of the cylinder (taking two actions), an then the M-32 is locked back together. In addition to the spring-loading, the M-32’s cylinder is gas-actuated. The cylinders rotate as a revolver, but the shooter can use a manual override in order to skip over dud rounds. This feature also allows the shooter to have different types of ammunition loaded into the cylinders, and choose which type of round he wishes to fire. The trigger is double-action-only; while this virtually eliminates the chances of an accidental trigger pull, it also makes the trigger pull very heavy. Barrel length is 14 inches.

There are a number of differences between the MGL Mark 1 and the M-32. The M-32 uses four MIL-STD-1913 rails instead of the single proprietary sight mount of the MGL Mark 1; these rails are atop the receiver/barrel and on the sides and bottom of the barrel, with the barrel being partially surrounded with a handguard for this purpose. (The Marines normally use a detachable handgrip on the lower rail.) The Armson Occluded-Eye Gunsight of the MGL Mark 1 is replaced with a similar, but detachable design made by Trijicon; this sight is an adjustable reflex sight with a slight magnification, and has an illuminated quadrant grid reticle to assist in aiming. The cylinders of the M-32 are longer; this allows the shooter to use almost the entire inventory of 40x46mm rounds (any round 140mm or less in length), including most pyrotechnics, flares, star shells, and some upcoming advanced rounds. The folding stock of the MGL Mark 1 is replaced with a stock similar M-4 Carbine-type stock; made by Vltor, this stock has six sliding positions, has limited adjustment for the angle of the stock, and has a thick recoil pad. The M-32 is also finished in Gunkote SCK6, which is highly resistant to corrosion and wear.

Twilight 2000 Notes: The M-32 is not available in the Twilight 2000 timeline.

Notes: Though never given an official designation by the US military, and never considered more than an advanced prototype, this grenade launcher was one of the best-like grenade launchers used by special operations troops in Vietnam, especially the SEALs, who reportedly used up to 30 of them in combat. Army Special Forces managed to get a hold of up to five of them, and the Marines got two of them for use by their Force Recon units. This weapon resembled a giant short-barreled shotgun, with a tubular magazine below the barrel and the leaf-type sights which were borrowed from the M-79. The firepower was quite welcome and the SEALs especially had good things to say about the weapon. The stock was of wood with a thick rubber recoil pad, the barrel and receiver were made from steel, and the magazine tube and pump action were built of aluminum; despite the large size of the weapon, it was fairly light. Unfortunately, tests and production of this weapon did not continue after the Vietnam War, though lessons from the weapon were incorporated into the EX-41 (see above).