Photos: Heckler & Koch G11 ACR

Here are a selection of external photographs showing the H&K G11 submitted to the US Army’s Advanced Combat Rifle trials in the mid-1980s. You can watch our introductory video featuring two G11s here.

Note: While this collection of images covers only the externals of the G11, rest assured that if and when we get the opportunity we will follow this up with hi-res photographs of the weapon disassembled!  

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Right side view of the G11, note the muzzle plug inserted into the barrel (Matthew Moss)
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Left side view of the G11, note the small window in the magazine showing the follower spring (Matthew Moss)
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Close up of the right side of the G11’s fire selector (safe – semi – hyperburst – full auto), trigger and grip which enclosed a ‘control brush’ used to check the chamber was empty and in cleaning (Matthew Moss)
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Left side close up of the G11’s selector, trigger and pistol grip – note also the rifle’s designation,  serial number, presumably manufacturing date and calibre moulded into the weapon’s casing (Matthew Moss)
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A view of the G11 from above – note the alignment of the magazine and the lack of later additional channels for spare magazines seen in some G11K2s (Matthew Moss)
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Close up of the G11’s foregrip and sling loop and an empty magazine loaded into the weapon  (Matthew Moss)
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Close up of the weapon’s rotating ‘cocking handle’and pressure valve, note the white arrow indicating the direction to twist the handle to cock the weapon – the plastic folding handle on this example has sadly broken off, a common issue with G11s (Matthew Moss)
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Close up of the left side of the G11’s ‘central part’, as HK described it, into which the barrel and breech assembly slide (Matthew Moss)

Many thanks to the collection, which wishes to remain anonymous, that holds this example of the G11 for the opportunity to examine, photograph and film it.


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2017.

An Introduction to the Heckler & Koch G11

Vic kicks off his series looking at the US Army’s ACR trials rifles with a look at, not one but two versions of, Heckler & Koch’s advanced caseless ammunition assault rifle – the G11. This video is an introductory overview, we’ll be delving into the G11’s insanely intricate and wonderfully complex action in later videos!

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HK ACR 4.92x34mm G11 (Matthew Moss)

There are few experimental weapons that have cultivated myth and reputation like Heckler & Koch’s G11. The product of decades of research and development into what was hoped would be the next evolutionary step in small arms design. The G11 was Germany’s attempt to combine advanced caseless ammunition with a weapon system which could increase the average infantryman’s hit probability. The G11’s action has three distinct modes of fire and uses a complex action and buffer/recoil system to achieve a high rate of controlled fire.

The program began in the late 1960s as part of a NATO initiative, however, it became a primarily Bundeswehr project and over two decades the design evolved substantially. The project sought to increase the hit probability of the individual infantryman. Heckler & Koch’s approach to this problem was the most radical. Working with Hensoldt to develop an integrated optical sight and with Dynamit-Nobel to create a new kind of ammunition.

Numerous studies and theoretical designs were worked up but by the mid-1970s the base design of what would become the G11 was cemented. The design team included Gunter Kastner, Dieter Ketterer, Tilo Moller and Ernst Wossner – all of whom are credited in H&K’s 1976 patent protecting the G11’s rotary action.

The G11 went through dozens of iterations throughout the 1970s and 80s, with the first firing prototypes ready by 1974. Both the design and the ammunition also went through a number of changes.

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Diagram showing the composition of the G11’s caseless ammunition (source)

The revolutionary ammunition was developed by Dynamit-Nobel AG.

The 4.73x33mm round which was finalised comprised of a solid propellant material body which encased a primer, booster, projectile and a plastic nose cap. Dynamit-Nobel developed the High Ignition Temperature Propellant (HITP) in an effort to prevent accidental ignition (cook-off) of the ammunition’s outer propellant body.

The G11 fed from 45 or 50-round horizontal, single stack box magazines which fed rounds into the action at 90-degrees. The rounds were then rotated into alignment with the breech by the rifle’s action.

The rectangular shape of the Dynamit-Nobel ammunition was more efficient and better suited to storage than conventional circular rounds. The positioning of the magazine along the top of the weapon, parallel to the barrel, also in theory helped minimise the rifle’s profile and reduce encumbrance for the soldier equipped with the weapon.

The G11 is a gas-operated weapon with gas being tapped from the barrel, to cycle the rifle’s cylinder drive system, which rotated the breech through a series of cams and gears. At the heart of the G11 is a complex rotary action. Rotating actions themselves are not a new concept with the earliest dating back to the 17th century, such as the Lorenzoni system.

The G11’s rotating breech was patented in late 1976 by Heckler & Koch. While our initial video does not go into detail on how the G11 operates, we will be covering this in later videos, this article will explain the action in more general terms.

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H&K’s early patent showing the G11’s rotating action – note the early incarnation of the ammunition with the projectile protruding from the propellant block (source)

Below are two diagrams showing the internal layout and major components of the G11 from a March 1982 draft of the ‘Rifle, 4.92mm, ACR’ armourer’s manual (source). It shows the major assembly groups and also a component list for the breech assembly.

From the diagram we can see the various action parts which feed the projectile into the breech, lock the action and ignite the round. We can also see the counter-recoil system beneath the barrel.

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The G11 used a counter-recoil buffer mechanism to allow high rates of burst fire. When firing three round bursts the weapon send the rounds downrange at a rate of ~2,000 rounds per minute, only when the last round has left the barrel does the barrel and action begin to recoil inside the stock along a central guide. When in sustained fire the rate of fire is closer to ~460 per minute.

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H&K promotional diagram showing the G11’s mounted recoil system (source)

The buffer spring below the barrel is compressed as the recoiling barrel and breech assembly moves. In sustained fire the buffer spring is partially compressed with each round, but in burst fire the buffer is compressed to its maximum hitting before the buffer housing (which is when recoil from the burst is felt by the operator), this is described as having the barrel and breech assembly ‘float’.

To ready the weapon to fire a magazine was loaded into the magazine channel on top of the G11, a magazine dust door, which automatically closed when unloaded, was depressed as the magazine was pushed home. The cocking handle on the left side of the butt was then actuated. The operator rotated the handle 360-degrees counter-clockwise until the weapon was cocked (essentially like winding a clock). The same process will eject any rounds left in the chamber once the magazine has been removed.

Gas tapped from the barrel cycles the cylinder drive system with gas pushing a piston back to act on a series of gears which rotated the rotary breech from horizontal to vertical to allow a new cartridge to drop into the breech. There was a vent for high pressure gas underneath the butt stock this prevented pressure build up and mitigated some of the thermal build up.

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Members of the Gebirgsjäger (Bundeswehr alpine light troops) on the march with G11s (source)

The G11 K1 was tested by the German Army in the late 1980s with adoption planned for the early 1990s. Heckler & Koch continued to develop the G11, entering the G11 K2 into the US Army’s Advanced Combat Rifle (ACR) trials alongside entries from Steyr, AAI and Colt [all of which we will examine in upcoming videos]. However, the fall of the Berlin Wall in 1989 and the collapse of the Soviet Union in 1991 meant that West Germany no longer had the huge amount of funds needed to field the G11. At the same time the ACR program ended inconclusively and the G11 project was finally abandoned.

The extreme complexity of the design, the inadequacy of the weapon’s ergonomics and its inevitably high production cost casts doubt on whether the G11 would ever have seriously been considered for widespread adoption. Regardless of this the G11 is a fascinating footnote in small arms history representing a false start along a technological avenue which, with the Lightweight Small Arms Technologies (LSAT) program, may still prove fruitful. Heckler & Koch and Dynamit-Nobel’s ambitious design marks one of very few serious and potentially successful attempts engineers to overcome the plateau that firearms technology is currently stuck on.

Technical Specifications (from 1989 H&K Brochure):

Length: 75cm (29.3in)
Weight (unloaded): 3.8kg (8.4lb)
Barrel Length: 54cm (21.3in)
Action: Gas-Operated, rotary breech
Calibre: 4.73x33mm
Feed: 45 or 50-round, single stack, box magazine
Cyclic Rate: sustained fire: ~460rpm /  3-round burst: ~2,000rpm


Bibliography:

Die G11 Story. Die Entwicklungsgeschichte einer High-Tech-Waffe, W. Seel, 1993

‘Shoulder Arm with Swivel Breech Member’, US Patent #3997994, 21 Dec. 1976, (source)

‘Automatic or Semi-Automatic Small Arm’, US Patent #4078327, 14 Mar. 1978, (source)

From the Small Arms Review Archive:

HK G11- ACR. Armourer’s Manual for Maintenance of Repair of Rifle, 4.92mm, ACR, March 1989 (source)

‘Rifle, 4.92mm, ACR’ Operator’s Manual (source)

HK G11 Caseless Ammunition Weapon System. The G11 Rifle. HK Factory Brochure, 1989 (source)

Our thanks to the collections that hold these examples of the G11. While one wishes to remain anonymous, we would like to thank the Dutch Military Museum for access to their G11.


Please do not reproduce photographs taken by Matthew Moss without permission or credit. ©The Armourer’s Bench 2017.