The LMT M203-2003 Grenade Launcher

The LMT M203-2003 Grenade Launcher


ABOVE: Shown is the M203-2003 mounted to the Dane’s issue Colt Canada IUR 5.56mm rifle. This soldier is using the standard leaf sight; however the rifle is to use the AimPoint sight as well.

The M203 grenade launcher has been in continuous service since 1968.  It was developed during the Vietnam War to get the grenadier into the battle when his launcher was either out of grenades or in an area where it would be ineffective.  The grenadier armed with a standalone M79 grenade launcher was considered a man down in an ambush or firefight because he did not have a rifle.  The thought was to combine both the grenade launcher with the M16A1 rifle.  Now we have severely increased the firepower on that individual level.  That concept has been in place ever since.

The M203 is the poster child of simplicity.  It is a slide action single shot launcher with very few parts and very little to go wrong.  The M203 developed a reputation for reliability with a service life of up to 10,000 rounds and an effective range of 350 meters.  The well trained grenadier could fire up to 7 grenades per minute.  The launcher weighs 3 pounds and is manufactured from 7075 T6 aircraft aluminum, same as that of the M16/M4 series of rifles.  The M203 has been adapted to both the M16 series rifles as well as M4 series of carbines.  It has also been adapted to many other weapons systems throughout the world.  The M203 has been manufactured by many companies throughout the years including Colt, Colt Canada/Diemaco, U.S. Ordnance, Airtronic USA, RM Equipment, Knights Armament Company and Lewis Machine & Tool.

This Danish soldier got brave enough to fire the M203-2003 in a pistol configuration by removing the stock assembly. He is experimenting on shooting without the benefit of sights.

The standard M203 launcher attaches to an M16/M4 series rifle via a locator pin on the rear of the launcher that index on the scallop of the barrel nut.  Then the front of the launcher is bolted to the barrel.  It bolts under the handguard on the rifle and on the carbine to a step cut in the barrel in front of the front sight base.  The three screws that lock the launcher to the barrel are then held in place with braided safety wire.  There are various types of handguards that go on the top of the launcher.  One is the standard rifle top handguard, which has the leaf sight attached to the top.  Also the top of the M4 and M5 RAS can be installed with a detachable leaf sight.  The carbine has a similar one-piece handguard with a mounted leaf sight as well as a modified round top handguard with the leaf site mounted on top.

The leaf sight is very simple with 50 yard increments from 50 to 250 meters.  The site can be adjusted via screw driver for elevation and windage for zeroing.  The detachable leaf sight mounts to the top Mil-Std 1913 rail.  The leaf sight is lined up with the front sight post for the sight picture.  Keep in mind grenade launchers are area weapons, not precision weapons.  Being able to determine distance is a critical skill of a good grenadier.

Shown is the LMT Guardian 2000 rifle with a standard M4 profile 14.5-inch barrel equipped with a LMT manufactured standard M203 grenade launcher with the 12-inch standard length barrel. This model grenade launcher has been sold to the U.S. Army as well as the Navy not to mention foreign military sales.

The rear quadrant sight is far more precise than the leaf sight.  Mounted to the carrying handle, the sight has a fold out peep sight and front sight post, which are both adjustable.  There are two mounts for the quadrant sight.  One is for the fixed M16/M16A1 and M16A2 carrying handle.  This one is now obsolete.  The second mounts to all the fixed carrying handles as well as the detachable carrying handles of the M16A4 and M4 series rifles and carbines.  The range of these sights is also in 50 meter increments but it ranges from 50 to 400 meters.  This is the preferred sight but these days not practical due to the use of optics on the weapons.  Reed Knight came out with a quad sight that mounts on the left side of the Mil-Std 1913 handguard.

The barrel comes in both 9- and 12-inch lengths.  The barrel has 6 lands and grooves with a right twist and 1 turn in 48 inches.  Inside the chamber are two cartridge holders that hold the grenade into the barrel.

By unscrewing four Torx bolts, the stock assembly is removed from the frame offering a pistol grenade launcher. Although a little on the uncomfortable side to fire, it is compact and effective.

The cycle of operations is quite simple.  On the top of the barrel is a barrel extension.  When the barrel is slid forward, the follower is pulled forward cocking the firing pin to the rear until it is held by the trigger.  The barrel is slid rearward until it is held in place by the barrel latch.  The trigger is pulled and releases the spring loaded firing pin/striker to hit the primer on the launcher, firing the High-Low Propulsion System grenade.  Once fired, the grenadier depresses the barrel latch and slides the barrel forward.  Several actions now happed.  First the extractor on the bottom of the launcher holds the rim of the case against the breech.  Once the cartridge case clears the barrel the spring loaded ejector kicks the fired cartridge case out of the breech of the launcher.  As the barrel continually moved forward the follower cocks the firing pin/striker.  Now the launcher is ready to be reloaded.

The grenades are very interesting in how the propulsion system works.  When the firing pin strikes the primer, the flash ignites the propellant in the brass propellant charge cup inside the high pressure chamber.  The rapidly increasing pressure reaches 35,000 PSI in the cup and ruptures at the vent holes.  The gas then vents into the low pressure chamber and the pressure is reduced to 3,000 PSI which propels the grenade through the bore to downrange.

The M203 grenade launcher first saw service in the early 1970s in the Vietnam War. The proven design has seen service all over the world and is in no danger of stopping. Simplicity and reliability is a true timeless design that never becomes outdated.

The 40mm round is very versatile, from practice rounds, to high explosive rounds to less than lethal rounds.  The standard M781 is a practice round that is filled with orange powder.  The M576 is a buckshot cartridge and there is a CS gas round for both military and law enforcement applications.  There are multiple high explosive rounds with the most common being the M397 Jump Up Fragmentation grenade and the M381 High Explosive grenade.  There are various parachute illumination flares as well as smoke grenades.  Less than lethal rounds consist of rubber ball, impact batons, foam impact rounds, barricade penetrator and distraction projectiles, to name a few.

Enter Lewis Machine & Tool into the M203 Market
In 1986, Lewis Machine & Tool (LMT) began production of M203 barrels for the U.S. Army followed in the early 1990s with production of receivers for the launcher.  Around that same time, Karl Lewis figured if they were making barrels and receivers, they might as well just make the whole thing.  From that point LMT manufactured parts as well as launchers under private labels of other defense manufacturers. In early 2000, LMT was awarded a contract for a large number of complete M203 grenade launchers for the U.S. Navy including the Naval Special Warfare Center.  In the intervening years, many sales of launchers have been sold throughout the world under the LMT name or under the label of the contracting company.  As of 2013, LMT manufactures a large number of grenade launchers under their own brand and sold throughout the world.  They also sell a large number under private labels as well.  They manufacture components for other manufacturers to put in their launchers.

Shown is the standard LMT M203 grenade launcher (top) as well as the new M203-2003 rail mounted grenade launcher (bottom). Notice the 12-inch barrel on the standard M203 and the 9-inch barrel on the M203-2003

In 2003, LMT introduced their first new launcher.  It is a M203 launcher but it is rail mounted.  This was done for the most part out of the requirements for the SCAR program.  At the same time, LMT introduced their MRP or Monolithic Rail Platform.  This was the industry’s first 1-piece upper receiver.  Due to it being manufactured from a single aluminum forging, the launcher could be mounted directly to the bottom rail, which is the Mil-Std 1913 rail.  Owing to the construction, the launcher never touches the free floating barrel.  In fact, any accessory could be mounted to the quad rails on the MRP with no ill effects on the barrel whatsoever.  The new M203-2003 launcher was a compilation of lessons learned from producing the standard M203.  Improvements in manufacturing techniques, materials and know-how made this even that much better than the standard run of the mill GI M203 grenade launcher.  The M203-2003 rail mounted launcher was modified to give an additional 3/8 of an inch more length to the open action allowing insertion of longer 40mm cartridges.  This was done by developing a different barrel stop.  The rail mounted launcher is held in with three Torx screws.  There are three stop notches machined into the rail of the launcher as well as three additional screws that lock into the notches for positive retention.  Although this is rail mounted, you must be careful which rails you put them on.  There is a significant amount of recoil generated by the launcher and many rails, including rails with removable bottom rails, will not stand up to heavy use.  LMT recommends that it go on a stationary lower receiver for full service life.  These include the Colt Canada/Diemaco IUR and LMT MRP.  There have been some adapters as well made for AK-type rifles.  There are perhaps others but the factory has not tested them so they can not endorse their use and ability to withstand the recoil of the 40mm round.

The rail mounted M203-2003 is held onto the rail by three Torx T27 bolts, which can be assembled by an end user rather than only by an armorer such as that is required for the installation of the standard M203.

As with many products in the industry, what is old is new again.  Although the M203 replaced the M79 stand alone launcher, there are those out in the field who like to have a separate launcher from their primary weapon.  Taking this information, Lewis realized he could adapt his M203-2003 easily to a standalone launcher – so he did.  The stand alone launcher he developed was a real update from the M79.  It has a telescopic SOPMOD stock with six positions as well as four quick detachable sling swivel mounts as well as a LMT Ergo pistol grip.  For those who really wanted it to be even more compact, the stock assembly can be easily removed by the user to create a pistol launcher.  Although not comfortable to shoot, it is still quite effective and compact.  LMT created their own leaf sight.  Slight modifications to the standard leaf site had to be made due to the different distance between the muzzle and the sight: the longer distance between the muzzle and the sight when mounted on a rifle versus just a launcher.  The leaf sight had to be moved back farther on the standalone launcher.

One of the latest sales of the M203-2003 was to the Danish Army.  Trials were conducted with all the major launchers including the M320 that has replaced the M203 in the U.S. Army as well as the Colt Canada Eagle grenade launcher.  The Danes found that the benefit of double strike capability did not offer enough of an advantage over the M203 design because the trigger pull was so heavy it affected the accuracy of the launcher.  The trials showed the Danes clearly that the double action triggers caused a “jerk” that affected accuracy.  The M203-2003 also allowed the use of longer rounds than that of the standard M203, which was an added benefit.  They also had the requirement for the standalone launcher, which the launcher was specifically designed.  Their requirement was the use of an AimPoint red dot sight over traditional leaf and quadrant sights.  They did want the leaf as more of a back-up sight.  The rifles issued by the Danish Defense Force are the Colt Canada/Diemaco C8IUR (Integrated Upper Receiver), which is a one-piece upper receiver.  The M203-2003 fit with no issues.  Testing showed there were no failures with the LMT launcher even after 400 rounds of plastic training rounds were fired through a single launcher without any issues.  After the award was won, deliveries commenced in early 2013.

The AimPoint red dot sight mounted to a Swedish made SPUHR mount. The quality of this mount is extraordinary with fine machining like a Swiss watch. The mount is ambidextrous and equipped with tritium lamps to assist in adjustment in low level light. This was the chosen mount for the Danes as well as this optic. They will use the leaf sight as only a back-up sight

The setup of the optics chosen by the Danes was quite interesting.  They procured a mount manufactured by SPUHR out of Sweden.  Upon examination of this mount it looked like a precision well made instrument.  Extremely high quality and well thought out.  This is an ambidextrous mount and requires no extra parts for making the change from one side or the other.  For low light situations the mount had tritium inserts at the 100/200/300 meter settings so the user can easily adjust for range even in darkness.  The mount has a built in spin drift compensation based on the customer specification and grenades that are used.  This mount is being utilized on both the rifle mounted and stand alone launchers.  The Danes are quite fond of the tan color so the launchers and stand alone units are delivered in the tan color.

With so much talk in the U.S. about having to replace 50+ year old designs, a very simple fact is overlooked.  If it worked well in 1968, it will still work well in 2013.  There are no expiration dates on these weapons.  Simplicity is a common thread in durability and reliability.  The M203, although being phased out in the U.S., still is being purchased throughout the world.  It is still beating these newer designs in testing and evaluations throughout the world.  Over these years the system has been improved right up through the release of the LMT M203-2003.  This is what breathes new life into this timeless design.  It should be expected this design will be in use for the next 50 years throughout the world.