By Jim Schatz
The advent of the low-velocity, dual-chamber 40x46mm spin-stabilized grenade in the early 1960’s brought easily portable and accurate long-range high explosive bursting capability to the individual combatant. With the introduction of the spin-stabilized grenade the modern foot soldier was no longer limited to short-range, hand-thrown grenades or the relatively inaccurate muzzle-mounted rifle grenades to deliver explosive ordnance to targets on the battlefield. The stand-alone U.S. M79 grenade launcher, first issued to U.S. forces in 1961, was quickly followed by the concept of the add-on grenade launcher only a few years later. The first known example of a single-shot SPIW type add-on 40mm grenade launcher appeared as a prototype in 1963 mounted on an AR-15 rifle. By the late 1960’s various early prototypes of an add-on launcher for the M16 rifle were already in existence. In August of 1969 after extensive testing the “XM203” became standard issue as the M203. Before production ended more than 100,000 M203’s had been produced for and delivered to the U.S. military.
The capabilities of 40X46mm spin-stabilized grenade added a new capability to the assault rifle. The infantryman could now engage area targets with high explosive grenades out to ranges of 400 meters, leaving the rifle to perform primarily point target engagements. The ballistic characteristics of the relatively slow moving grenade provided the combatant with at least a degree of ability to engage targets in the defilade. Unlike muzzle-mounted rifle grenades, the 40x46mm grenade can be comfortably fired from the shoulder and does not require special launching cartridges.
There is an almost unlimited selection of 40x46mm grenades available around the world today. In the U.S. military alone at one time more than 25 issue grenades were type classified. These included the standard M433 HEDP (High Explosive Dual Purpose) and M781 TP (Training Practice) rounds that are still standard issue today. In addition a host of assorted special-purpose rounds have been and are still available to include pyrotechnic (CS gas, smoke and illumination), short-range, anti-personnel rounds such as flechette and buckshot rounds, less-than-lethal bean bag and sticky foam grenades, infrared illumination grenades, flash bang rounds, incendiary, tracer, fragment-free high explosive “offensive” grenades, hollow charge rounds for armor penetration, air-bursting grenades, and many more.
The concept and tactical advantage of the 40mm grenade launcher is a concept that was not lost on most of the other nations in the world, free world, third world and our former enemies behind the iron curtain. There are no less than 13 different stand-alone and add-on grenade launchers available today firing the 40x46mm or former Soviet B40 30mm spin-stabilized grenade. Certainly the genesis and success of the high-velocity 40x53mm grenade designed for use in grenade machine guns like the US MK19 owes at least part of its success to the combat capabilities first afforded by the 40mm shoulder-fired grenade launcher.
Spin stabilized “potato mashers” in Germany
In Germany, the Bundeswehr has been somewhat slow in their adoption of a shoulder-fired 40x46mm grenade launcher. The Heckler & Koch 40mm HK69A1 “Granatpistole” (grenade pistol) did not become general issue until 1975 after a great deal of testing and design evolutions. In some way a modernized version of the U.S. M79, the HK69A1 has been rated as the most accurate shoulder-fired grenade launcher by experts such as the late Dr. Ed Ezell, the late Curator of the Armed Forces Division of the Smithsonian Institution.
The HK69A1 is still carried today by the German military grenadiers in addition to the primary weapons, either the G3 or newer G36 assault rifle. The HK69A1 with its retractable buttstock can be fired from the shoulder or as a pistol and is carried using a detachable carrying sling or in a large polymer thigh holster. Though Heckler & Koch has offered an add-on 40mm grenade launcher called the HK79 for the HK assault rifles, namely the G3, HK33 and discontinued G41, the additional weight of adding a 3.4-pound grenade launcher to an already heavy 10-pound G3 has not inspired the Bundeswehr to turn in their HK69A1’s. Like most stand-alone grenade launchers the HK69 simply provided too much accuracy to be replaced by an add-on launcher as it is easily aimed and fired much like a rifle with consistent repeatable accuracy.
The sighting systems and ergonomics of most add-on grenade launcher simply cannot match the rifle-like feel and sights of a U.S. M79 or especially the more user friendly HK69A1. This fact not withstanding, the HK69A1 and a police variant called the MZP1 and HK79 have been adopted by military and special law enforcement organizations around the world for delivering both lethal and non-lethal 40mm ordnance.
Along comes the new G36
In the early 1990’s the Germany Constitution was changed to allow German troops for the first time since the end of World War II to deploy on foreign soil, in modern times as equal members of the NATO peacekeeping forces. The need for a modern assault rifle in the now commonly issued 5.56x45mm NATO caliber spawned the need for a replacement to the venerable G3 that had served the Bundeswehr well for more than three decades. In 1996 after extensive design and testing the German military adopted the new HK G36 Rifle to replace some or eventually all of the G3’s in German service.
Almost immediately a requirement surfaced for a lightweight modern 40mm add-on grenade launcher for the equally modern and lightweight G36 rifle. By 1998 work had already begun at HK GmbH in Oberndorf on a new grenade launcher that would become known as the “Anbaugeraet” AG36 (literally translated as “Additional implement” or “tool”). Tool is right, and a very capable tool at that.
The AubauGeraet 36
Now that we have arrived at the genesis of the current state-of-the art add-on single shot grenade launcher from Heckler & Koch let’s take an in depth look at this new creation. Like all add-on grenade launchers the AG36 was designed to be a secondary weapon attached to the primary assault rifle, or in some cases to submachine guns. The AG36 is attached to the weapon in the classic position below the barrel where the forearm or handguard is generally located. Unlike most add-on grenade launchers however the AG36 is designed to be easily removable by the operator allowing him or her the option of adding the launcher to the rifle when the mission requires it.
The AG36 is attached to a modified G36 forearm that will fit on both the full size G36 Rifle and shorter G36K Carbine. The forearm provides two mounting holes through which a special large detachable locking pin, typically of the HK weapons system, can be inserted. The front hole is used for the rifle, the rear for the carbine.
The AG36 attaches to the weapon at two points, the front of the receiver like the standard forearm and through the gas block, which is semi-permanently pinned to the barrel of the weapon. To secure the launcher in place once fitted to the receiver the special locking pin is inserted through the appropriate (and marked) forearm hole and the gas block. This mounting system eliminates the need for armorer’s involvement to attach or detach the launcher and leaves the barrel free to float so as to not disturb rifle accuracy when mounted.
When detached from the rifle the AG36 is complete and can thereby be fired off of the host weapon. When employed as a true grenade pistol the recoil is pronounced but not uncomfortable if handled with the respect it deserves. While accuracy is severely affected when hand firing a 40mm grenade launcher this can be done. The accuracy or lack thereof would be quite acceptable when launching pyrotechnic rounds or fragmentation grenades at relatively short ranges (under 150 meters). It is expected that an add-on buttstock with sight mounting rail will be available in the future so that the AG36 may be shoulder fired off of the host weapon.
The design of the AG36, like the host rifle, uses polymer materials in the non-pressure bearing components of the launcher such as the vertical foregrip, forearm, most of the operating controls to include the trigger, safety/selector lever and breech release button as well as the mechanical sights themselves. The 11-inch rifled barrel is fashioned from aircraft-grade aluminum to be light in weight, a departure from earlier HK grenade launchers that employed, at a substantial weight penalty, steel as barrel material for its increased strength. The receiver is produced using mostly aluminum alloy with a steel insert surrounding the firing pin opening.
The launcher operation can be described as a breech-loading single shot. The spring-actuated barrel opens positively to the left side of the receiver when the ambidextrous breech release button, located in the top inside corner of the trigger guard, is actuated by the thumb or forefinger. This set up places the operator’s hand at the correct position to remove the live round or fired casing from the barrel as soon as the barrel pops opens. The live round or spent cartridge case is removed manually by the operator rather than by employing a complicated auto ejector into an otherwise simple design.
Like all HK grenade launchers the barrel is opened and closed manually and without automatically cocking the firing mechanism. This feature reduces the chances that a live round could be fired inadvertently. An opening in the launcher’s aluminum frame provides the means to force the breech open by hand should this be required in the event the spring-actuated barrel is jammed by an out-of-spec or overpressure round or by severe climatic conditions such as extreme cold or freezing rain.
An advantage of the side loading breech design employed in the AG36 is that any length grenade can be fired from the launcher, even those that protrude from the muzzle. There are many highly desirable pyrotechnic 40x46mm rounds that simply cannot be fired in sliding barrel designs such as the US M203.
Double-Action-Only Firing Mechanism
The AG36 introduces a Double-Action-Only trigger cocking system wherein the firer simply pulls the trigger to cock and automatically release the internal hammer. This eliminates a separate external cocking device or hammer and thus an additional step required for firing. The DA-Only trigger system allows a hard primer to be struck multiple times in the event of a misfire, something that occurs more often in harsh and especially cold-weather environments. The absence of external hammers and cocking devices also improves the safety of the weapon when dropped or during rough handling as the striker of the DA-Only AG36 is always at rest unless the trigger is pulled. The pressure required to cock and release the internal striker is approximately 12.5 pounds.
For additional safety an ambidextrous safety/selector lever is provided to the rear of the breech face. The device blocks the movement of the trigger and release of the hammer until set in the “F” position for firing. A fixed, vertical pistol grip, while at first somewhat unconventional for an add-on grenade launcher, provides for a more solid grip on the launcher and moves the hand off and away from the hot barrel during extended firing sessions.
40mm low-velocity grenade launchers are considered by most users as area target weapons and thus are not expected to provide repeatable pinpoint accuracy. The old adage of “close is close enough” is acceptable when firing high explosive ammunition on open terrain with a 5- to 15-meter bursting radius. The slow exit velocity (approximately 250 fps) of the 40x46mm grenade requires a steady hand, good trigger control and sufficient follow-through to produce good accuracy. Any abrupt movement of the weapon during the final aiming process can have an adverse effect on the undisturbed launch of the grenade from the barrel.
Users will most always demand the maximum amount of accuracy possible from any type of firearm. A combat pistol should shoot like a competition match gun, an assault rifle like a sniper rifle, and so on. The same enhanced performance characteristics are applied to area weapons also by demanding users. There are many times when the precise placement of a single grenade is tactically advantageous and thus the launcher must be provided with sights that are up to the task at hand if the launcher and ammunition are as well.
The HK designers realized this and included a modular sighting option for the AG36.
Two sighting options are currently available for the AG36. Both can be mounted on either the right- or left-hand side of the weapon by the operator without special tools, using only an Allen wrench. This allows a great deal of flexibility to accommodate the shooting preferences of the shooter. It is also possible to mount both sights on the weapon at the same time, though it is doubtful anyone would.
The mechanical sight for the AG36 is a standard flip-up ladder sight as employed on other 40mm launchers to include the US M203. These sights can be attached to the left or right sides of the AG36’s integral forearm to threaded hard points molded into the polymer material. This leaves the top of the weapon open for sights and other optional targeting devices so common on military rifles today. This arrangement also insures that the launcher’s zero is retained when it is removed from the host weapon and remounted at a later date to the same or even a different rifle altogether.
The Patridge-style mechanical sights are adjustable for windage and elevation, using a 3mm Allen wrench and provide a 5.8-inch sight radius, a sufficient set up for average grenade launcher accuracy. Aiming windows are provided around the rear sight notch for 50- to 350-meter ranges in increments of 50 meters and are, of course, offset to the right to account for the right-hand drift of the slow-moving and right rotating spin-stabilized 40x46mm grenade.
For users requiring enhanced accuracy and uninterrupted 24-hour usage, HK offers an optical or “Glass Block” reflex sight for the AG36 that attaches to the standard mounting points in the rear of the rifle’s carrying handle. Like the mechanical sights the bracket of this sight allows it to be mounted to the right or left side of the optical or iron sights.
Where the mechanical sight offers the user light weight, simplicity, little additional mass and low cost but limited accuracy and flexibility the Glass Block sight provides much better accuracy and consistency than is possible with the mechanical sights. The reticle of the Glass Block sight, produced by the Ring Sight (E.P.C.) in the U.K., provides a vertical “ladder” reticle pattern for target engagements from 50 to 350 meters, once again in increments of 50 meters. Because the image of the reticle pattern is presented within a glass block the operator need not close his or her eye to see it. As there is no requirement for aligning a front or rear sight and the target, aiming the AG36 with the Glass Block sight is simple, fast and very repeatable. The white aiming dots within the reticle are small enough to provide the necessary precision yet are picked up easily, even during low light periods due to the presence of a tritium source that illuminates the reticle pattern under periods of darkness. A precise 24-hour non-battery powered sight for a grenade launcher. Who could want for more?
New hosts for the AG36
Almost as soon as the AG36 was announced for the G36 rifle potential buyers for the launcher began to appear. Not only have the German and Spanish armies expressed obvious interest in the AG36 for their issue G36 rifles but orders have materialized for the features and capabilities of the AG36 on rifles other than those from HK. This is not surprising as previous HK add-on grenade launchers, such as the HK79A1, were adapted for use and fielded on the British SA80 rifle and the US M16 rifle and M4 Carbine for foreign customers. In fact the HK79A1 was selected as the technically superior candidate after extensive testing for the Canadian C8 rifle but lost in the end to a less expensive homegrown alternative.
Recently, the British MOD announced that they would be purchasing 1,000 Canadian C8 Carbines in the U.S. M4A1 configuration with the Rail Interface System for issuance to their Special Forces personnel. After extensive comparative testing a variant of the HK AG36 was selected for the new British SOF carbine. This AG36 variant attaches to the lower MIL-STD-1913 rail located at the 6 o’clock position on the Rail Interface System. Outside of this change the launcher itself remains basically the same. When completed, this version of the AG36 will be compatible with any assault rifle, to include the US M16 and M4A1 rifles that provide a firm mounting point meeting MIL-STD-1913 dimensions below the barrel.
The future for an advanced lightweight add-on grenade launcher like the Heckler & Koch AG36 appears bright indeed.
|This article first appeared in Small Arms Review V6N10 (July 2003)|