In the second video Matt tackles the Heckler & Koch G11 and gives an update on the colouring book and the channel:
Thanks for watching chaps & thanks so much for your support in 2019, we greatly appreciate it. It’s been a busy year and we hope that you’ve all enjoyed our videos!
You can still pick up a copy of the ACR colouring book and the G11 sticker at www.armourersbench.com/shop. we’re very much looking forward to seeing your artistic sides when you send us some photos of your colouring to – contact@armourersbench.com.
The Armourer’s Bench are proud to introduce our very first ‘informative colouring (coloring) book’. Not only can you colour in the prototypes from the US Army’s Advanced Combat Rifle trials but you can also learn about the guns, how they worked, performed and the outcome of the trial as you colour!
Why a colouring book? Well, simply put, no one else has done one before! With the help of our brilliant illustrator, Lauren McInnerney, we put the book together to give you guys something a bit different, something fun!
We have a limited run of these little books and we will do our very best to get them our ASAP if you order them for Christmas.
The book includes detailed original illustrations of each of the four ACR guns: the AAI, Colt, Steyr and of course the iconic HK G11. The 8-page booklets are 8×6″ (or A5 sized) and are available now from our website for $6.00, plus shipping.
All the funds raised from the sale of the books will go toward supporting TAB through 2020.
But wait! That’s not all! We also have some extremely cool new stickers available. These 4″ cutout vinyl stickers feature the TAB logo on an illustration of the G11.
And last but not least we also have a small run of TAB logo badges available too!
Here’s Vic’s video on the XM148, check out Matt’s article below:
There have been attempts to fire grenades from the infantryman’s weapon since the 17th century. Up until the 1960s these almost entirely involved muzzle attachments or grenades which could be fired off the end of a rifle’s barrel. In May 1963, the US military called for a new ‘underslung’ grenade launcher to complement the AR-15/M16, then in early testing. The grenade launcher program had its roots in the ultimately unsuccessful Special Purpose Individual Weapon (SPIW) program which had begun in 1952.
While a series of designs were developed by various manufacturers and designers, May 1964 saw Colt unveil the CGL-4. The Colt was tested against designs from Springfield Armory and Ford, a design from AAI was promising but it was not able to chamber the 40x46mm rounds used by the M79 and was rejected. The US military sought munitions commonality between the M79, already in service, and the new rifle-mounted grenade launcher.
Left side view of the XM148’s bulky tangent sight (Vic Tuff)
In March 1965, the CGL-4 was chosen for further testing and a contract for 30 launchers was signed. The CGL-4 was reportedly developed by Karl Lewis and Robert E. Roy in just 48 days. However, the design was complex. To load the barrel housing slid forward allowing a grenade to be placed in the breech, the weapon was then cocked and a long trigger, which projected back towards the rifle’s trigger guard, could be pulled to fire the weapon.
Karl Lewis & Robert E. Roy’s patent for the Colt CGL-4 (US Patent Office)
Despite some problems with barrel housings cracking an order for 10,500 of the new launchers, now designated the XM148, was placed in January 1966. Production capacity issues and problems with the launcher’s sight lead to production delays and it wasn’t until December 1966, that the first shipment of 1,764 launchers arrived in Vietnam for field testing.
Right side view of the XM148’s trigger, cocking mechanism and pistol grip (Vic Tuff)
Initial reports from the field were promising with troops praising the “tactical advantage of both the point fire and area fire system” concept. The XM148 was well received by the SEALs and the Australian SAS. The armourers of the Australian SAS, deployed to Vietnam with the 1st Australian Task Force, were also hard at work attaching XM148s to L1A1 rifles. Removing the L1A1′s handguard and attaching the XM148 to the rifle’s barrel.
Field testing was carried out by 12 units from six different divisions which were operating in various parts of Vietnam. This gave a wide variety of terrains and yielded some interesting results. In general it was found that the XM148 decreased rate and quantity of the grenadier’s fire, it slowed his reaction times when firing at a target, it hampered his movement in dense vegetation and also meant the grenadier had to spend longer caring for his weapon.
XM148 with breech open (Vic Tuff)
It was noted that the sight mount which was overly complex and prone to snagging on brush and kit, it was also felt that too much force was needed to cock the XM148 (around 30 lbs) and the trigger mechanism was felt to be overly complex and difficult to repair and disassemble. One safety concern was the XM148′s long trigger bar, which could snag and launch a round – not ideal for special forces patrols infiltrating through thick bush. Problems with the launcher’s quadrant sights also continued causing deflection errors out at longer ranges. The bulkiness of the sights exasperated these problems as when they were knocked the XM148′s zero could be effected. The XM148 also precluded the use of a bayonet as when fired it would blow the bayonet off the muzzle. Overall, troops felt the XM148 was too fragile and complex for use in the field.
SP4 Willey firing an M16A1 mounted with a Colt XM148 c. 1967 (US National Archives)
At least one unit found use for the launchers, the 1st Cavalry Division (Airmobile)’s Operational Report for Quarterly Period Ending 31 October 1967, noted that the XM148
“proved unsatisfactory in infantry units due to its lack of durability; consequently, USARV directed that they be turned in. However, 1/9 Cav has devised a method of mounting the launcher coaxially on the M60C machine gun used by scout observers on OH-13 scout helicopters. Durability in this environment is
not a problem since the weapon deos not receive the rough handling it did in the hands of ground troops. Firepower on scout helicopters is significantly increased. Fifty-two XM148s have been retained for use by 1/9 CAV.”
Finally, despite Colt’s efforts to rectify the growing list of problems the Army Concept Team In Vietnam deemed the XM148 unsatisfactory for deployment in Vietnam and recommended they be removed from service and a new improved launcher be developed. This was a massive blow to Colt who had already manufactured 27,400 XM148s. Many of these were already in Vietnam.
The US Army launched the Grenade Launcher Attachment Development (GLAD) program in the summer of 1967. A large number of manufacturers submitted designs including Colt, who offered the improved Henry Into-designed CGL-5. The Army turned down Colt’s offer of 20 free improved launchers and rejected the CGL-5 outright. The GLAD program saw the resurgence of the earlier AAI design, designated the XM203, this simple design, now chambering the 40x46mm shell, was eventually selected in August 1968. Ironically, as AAI was predominantly a research and development company and after an initial run of 10,000 made by AAI, Colt was subsequently awarded the contract to manufacture the M203 from 1971 onwards.
Harold Into’s patent for the product improved CGL-5 (US Patent Office)
While the XM148 proved to be a failure it played an important role in proving the operational viability of the rifle mounted grenade launcher system. The muzzle-launched rifle grenade is all but obsolete, superseded by the under-slung grenade launcher.
If you enjoyed the video and this article please consider supporting our work here.
Specifications:
Length: 16.5 inches
Weight: ~3lbs
Calibre: 40x46mm
Action: single shot, striker-fired single action
Capacity: 1
Rate of Fire: ~4 rpm
The AAI Corporation was founded in 1950, as Aircraft Armaments, Inc., and has long been involved in advanced firearms design, taking part in a number of the US military’s previous small arms programs. Throughout the Cold war AAI was involved in the US Army’s search for a new advanced infantry weapon system. Before we examine the AAI ACR, it is important to understand the context in which it evolved.
The Special Purpose Individual Weapon (SPIW) program, an off-shoot of Project SALVO began in the early 1950s and ran until the late 1960s. During the SPIW program AAI developed a series of designs, including an entire family of weapons, which used flechette technology. These culminated with the XM19 rifle, or SFR – Serial Flechette Rifle. The XM19 represented the pinnacle of over a decade of flechette technology development, however, the end of the US war in Vietnam saw the need for SPIW disappear and the program was wound down.
AAI SPIW family of weapons from the early 1960s (Reproduced in Stevens & Ezell’s SPIW Deadliest Weapon)
In the early 1970s SPIW essentially morphed into the Future Rifle Program, but with the end of US involvement in Vietnam, this also proved a failure. During the early 1980s the US Army awarded development contracts to both AAI and Heckler & Koch to develop caseless ammunition and a weapon system capable of firing it. While H&K G11 is no doubt the better known of the two weapons, AAI’s Caseless Weapon, while a move away from flechette technology, was also an interesting design.
AAI’s Caseless Ammunition Rifle, another image available here (US Army)
Firing a variety of ammunition the AAI design was capable of firing a high cyclic rate 3-round burst at 1600-1800rpm. The ACR program summary report noted that the AAI Caseless project was feasible and only lacked development funding to make it a reality, as the design was much simpler than the G11.
AAI were one of six companies to respond to the ACR program’s Request for Proposals, released in September 1985. AAI’s ACR was an evolution of the earlier SFR/XM19 rifle. The weapon AAI submitted was gas-operated, fed from a 30-round box magazine, and fired a brass cased flechette round in either single shot or a high cyclic rate three round bust – fired at a cyclic rate of ~1800rpm.
Left-side view of AAI Corporation’s ACR entry (Matthew Moss)Right-side view of AAI’s ACR entry (Matthew Moss)
AAI’s ACR fired from a closed bolt and used a muzzle device to reduce muzzle climb during burst firing. The 1990 ACR Program Summary report explains how the rifle’s gas system worked:
“…incorporate an ‘entrapped gas’ operating system. Gun gases enter a cylinder, drive a piston to power the system, and prevent any leakage of propellant gases and residues into the other mechanism parts.”
AAI developed a polymer saboted steel 10.2 gr ‘sub-calibre’ flechette which fitted within a standard M855 brass case. As a result the rifle used a proprietary magazine to avoid the accidental chambering of conventional 5.56x45mm rounds. The flechette rounds had a muzzle velocity of 4,600 ft/s with propellant produced by the Olin Corporation.
An AAI Corporation ACR marked serial number 20 (Matthew Moss)
The rifle was designed to mount a quick detachable 4x optic and also had a white-highlighted shotgun-style rib sight along the barrel to aid snap shooting. The rifle was one of the longest entries with an overall length of 40 inches or 101.6cm. Interestingly, rather than a push-button magazine release, AAI opted for a large paddle release.
The fore-end of the AAI ACR, note the front sight post and muzzle device which reduced muzzle climb during burst firing (Matthew Moss)
AAI’s rifle borrowed some of its external ergonomic characteristics from the M16A2, then in service. With a moulded polymer pistol grip and butt, forming part of the lower receiver, shaped to mimic the M16’s. It also utilised the M16’s sling loops and butt plate.
According to the ACR program summary the AAI entry proved to be a “mature design which performed in a reliable fashion” during the field trials. It was regarded as a weapon with known reliability with a flechette round superior to the Steyr, the other flechette-based entry.
Close up of the right-side of the AAI ACR, note the ejection port and moulded plastic case deflector, selector level, paddle magazine release and sight mount (Matthew Moss)
Today, AAI continue to develop both small arms and other defence technologies. Now a part of Textron, they are currently involved in the US Army’s Lightweight Small Arms Technologies (LSAT) program.
If you enjoyed the video and this article please consider supporting our work here.
Specifications (From 1990 ACR Program Summary):
Length: 40 inches / 101.6cm
Weight: 9.39 lbs / 4.26kg
Sights: Iron or 4x optic
Action: Gas operated
Calibre: 5.56mm brass cased flechette
Feed: 30-round box magazine
You can find out overview article on the ACR program and all of the rifle here.
Bibliography:
Advanced Combat Rifle, Program Summary, Vol.1, ARDEC, 1992 (source)
‘Revisiting the SPIW Pt. 1-3’, Small Arms Review, R. Blake Stevens, (123)
The SPIW The Deadliest Weapon that Never Was, R. Blake Stevens & E.C. Ezell (1985)
Our thanks to the collection that holds these wonderful examples of the ACR rifles
The four rifles tested during the final phases of the ACR program, AAI, Colt, H&K, Steyr (Matthew Moss)
With so few primary or secondary sources on the ACR program available, this article relies heavily on the 1990 program summary report written by the US Army Armament Research, Development and Engineering Center (ARDEC). Over the next three articles we will examine the AAI, Colt, and Steyr ACR entries. The H&K entry was covered earlier – here.
In the early 1980s the US Army began looking into what form a replacement for the M16A1 might take. The Joint Service Small Arms Program undertook a study and found that in the long term a “technology base should be developed to support a significant improvement in capability.” This meant the US infantryman’s next rifle would move away from conventional ammunition and actions.
The Advanced Combat Rifle program began in January 1985, to foster the development and select a rifle that would give troops a distinct advantage on the battlefield. The project’s ambitious aim was to address the human shortcomings of the average soldier in the field. It was found that combat stress, fear and fatigue negatively impacted on a rifleman’s ability to hit a target once engaged in combat.
US Army’s 1959 Future Soldier Concept, with M14 (LIFE )
The ACR program sought to compensate for this by maximising hit probability when engaging fleeting targets in battlefield conditions. The program called for:
“an enhancement in hit probability of at least 100 percent at combat ranges over the baseline performance of the M16A2 rifle… at extended ranges, the improvement required will be considerably greater than 100 percent. The weapon will be expected to enable the rifleman to detect rargets at ranges greater than 400m in offensive action and at least 1000m during the conduct of the defense.”
This was a tall order, calling for a weapon with an optic and the ability to engage long range targets, which were envisaged to be wearing body armour, but also engage fleeting targets. But the ACR program was far from the US military’ first ambitious small arms project.
The ACR program built on the Special Purpose Individual Weapon (SPIW) program that had been established in the 1950s to produce the next generation of infantry weapon capable of firing busts of flechettes at extremely high rates of fire to improve hit probability. This task proved technologically insurmountable during the 1950s and 60s. The SPIW program ended in the late 1960s, but was followed in the early 1970s by the Future Rifle Program which also proved a failure. Despite these failures the programs helped to push small arms technological boundaries.
In the video below, produced by ARDEC for the US Department of Defence, we see the ACR program briefly explained and the various rifles introduced with some firing footage:
The approaches used by the companies that entered the ACR competition varied greatly. Ranging from rifles with complex buffer systems to weapons that fired duplex and flechette rounds.
The first Request for Proposals was released in September 1985, with six companies successfully submitting proposals. These companies, which were awarded a Phase I contract, were: AAI Corporation, Ares Incorporated, Colt’s Manufacturing Company, Heckler & Koch (H&K), McDonnell Douglas Helicopter Systems (MDHS), and Steyr Mannlicher. In 1987, following Phase I of the program the entries from Ares and MDHS were dropped due to ‘hardware immaturity’ – the concepts were not developed enough. Both companies appealed and were allowed to enter designs to Phase II but neither was sufficiently developed to compete in the later trials and testing.
Each company approached the program’s aims in a different way. Two utilised flechette technology, which had been developed during the SPIW program, with the AAI using a brass cased round while the Steyr ACR used a polymer case. Colt’s entry used a duplex round with two projectiles stacked in the cartridge case. Heckler & Koch’s G11 used a complex buffer system to reduce felt recoil after firing a ‘hyper burst’ of three rounds at ~2,000 rounds per minute.
Lets take a look at the individual weapon systems:
AAI Corporation had long been involved in advanced firearms design, taking part in the US military’s previous programs. The AAI ACR was an evolution of the earlier SFR/XM19 rifle. AAI’s ACR was gas-operated, feeding from a 30 round box magazine and fired a brass cased flechette round in either single shot or a high cyclic rate three round bust.
It fired from a closed bolt and used a muzzle device to reduce muzzle climb during burst fire. AAI developed a polymer saboted steel 10.2 gr flechette which fitted within a standard M855 brass case. As a result the rifle uses a proprietary magazine to avoid the accidental chambering of conventional 5.56x45mm rounds. These rounds had a muzzle velocity of 4,600 ft/s.
Diagram showing AAI’s saboted flechette round inside a 5.56x45mm M855 case (US Army)
The rifle was designed to mount a quick detachable 4x optic and had a white-highlighted shotgun-style rib sight along the barrel to aid in snap shooting. The rifle was one of the longest entries with an overall length of 40 inches or 101.6cm.
According to the ACR program summary the AAI entry proved to be a “mature design which performed in a reliable fashion” during the field trials.
Specifications (From ACR Program Summary):
Length: 40 inches / 101.6cm
Weight: 9.39 lbs / 4.26kg
Sights: Iron or 4x optic
Action: Gas operated
Calibre: 5.56mm brass cased flechette
Feed: 30-round box magazine
Colt’s entry was perhaps the most conventional of the designs submitted. Based on the rifle the program sought to replace. Colt’s ACR was essentially an improved M16, which fired both conventional 5.56x45mm ammunition as well as a new 5.56mm duplex round. While the duplex round increase hit probability at shorter ranges, it impacted long range accuracy requiring the additional use of conventional M855 rounds.
It incorporated a variety of improvements including a new oil/spring hydraulic buffer to mitigate recoil. A reshaped pistol grip and a hand guard which mounted a sighting rib for snap shooting. The weapon had a flat-top upper receiver which was railed so a 3.5x optic (an early ECLAN) or a more conventional sight/carrying handle could be fitted.
Colt’s 5.56mm Duplex round (US Army)
The rifle’s collapsible six position telescopic butt stock was an improved version of that offered with Colt’s carbines. When at full extension the Colt ACR was the longest rifle tested, at 40.6 inch or 103 cm long. A distinctive proprietary muzzle brake compensator designed by Knight’s Armament was also added.
During testing one of the duplex rounds was not properly seated inside the cartridge case and when fired became lodged in the barrel and during the course of fire and the weapon’s barrel blew when another round was fired. This was addressed by a slightly larger propellant charge. Some of the features developed for the ACR entry were later employed in the M16A3 and later A4.
Specifications (from ACR Program Summary):
Length: 40.6 inches / 103cm (extended) and 36.7 inches / 93.2cm (collapsed)
Weight: 10.3 lbs / 4.67kg
Sights: iron or 3.5x optic
Action: Direct gas impingement
Calibre: 5.56mm duplex round & M855 ball
Feed: 30-round box magazine
Heckler & Koch had been involved in the West German Bundeswher’s attempts to create a next generation infantry weapon. The result was the G11, the G11 had been in development since the late 1960s and by the time it was entered into the ACR program it had evolved into a complex weapon unlike any other. Utilising a gas-operated, rotary breech to fire self-contained caseless 4.73×33mm projectiles. The rotary breech chamber was introduced as a means of clearing misfired, broken or defective cartridges from the enclosed system. Simplicity was sacrificed to achieve reliability.
The US had awarded H&K a contract to develop caseless ammunition, optics and the salvo concept in 1982. With the G11 in development they then entered the ACR program. The bullpup H&K was the shortest of the weapons entered into the trial at 29.5 inches / 74.9cm. It was equipped by a variable 1-3.5x optic designed by Swarovski.
Diagram showing the composition of the G11’s telescoped caseless ammunition (source)
The revolutionary ammunition was developed by Dynamit-Nobel AG.
The 4.73x33mm, 51gr 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 ACR program summary notes that “the majority of the malfunctions/stoppages experience in the field experiment were ammunition related.”
The H&K ACR fed from a single stack, horizontally orientated 45-round magazine which sat above the barrel.
The G11 used a counter-recoil buffer mechanism to allow high rates of burst fire – hyper burst. When firing three round bursts the weapon could 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. The recoil impulse was then quite strong. When in sustained fire the rate of fire is closer to ~460 per minute. A more detailed explanation of the G11’s action can be found here.
Steyr-Mannlicher’s bullpup entry uses a gas piston driven rising chamber mechanism which rises and falls to chamber rounds as the action cycles. The Steyr ACR, like AAI’s entry, fires flechettes but Steyr’s are housed inside a cylindrical polymer case. The bullpup Steyr was the second shortest at 30 inches (76cm) and the lightest of the rifles submitted weighing 8.5 lbs (3.86kg).
The Steyr ACR borrows its ergonomics from its conventional forebearer, the AUG. With a moulded green plastic stock and a similar pistol grip, trigger and safety layout. Unlike the AUG, however, the ACR uses an AR-15 style charging handle located at the rear of the sight mounting block. The rifle could be fitted with a variable 1-3.5x optic.
The rifle does not use a conventional bolt, instead it has a rising chamber, as a result the rifle fired from an open bolt. A live round only entered the chamber after the trigger had been pulled, thus reducing the potential for cook-offs. Spent polymer cases were pushed out of the chamber and ejected from an opening just in front of the magazine well.
Steyr’s Polymer Cased Flechette round (US Army)
Feeding from a 24-round box magazine, made from the same translucent material used in conventional AUG magazines. The magazine goes from double stack to single stack, to allow it to feed reliably, as a result the capacity had to be shortened. A high capacity drum magazine was planned but not provided for the trials. The polymer case held a fin stabilised 9.85 gr flechette with a moulded four piece sabot which broke up soon after exiting the muzzle. This was identified as a shortcoming as it risked hitting nearby troops.
After several years of development, while the Army organised testing, the four firms delivered their prototypes in 1990. During Phase III the rifles were tested on the specially built Buckner Range – designed to recreate field conditions and create fleeting targets at various ranges. The M16A2 was used as a baseline weapon throughout all of the tests which included safety and engineering testing, lethality tests and testing in field conditions.
Initially planned as an all-services test both the US Navy and Marine Corps pulled out of the ACR program in 1987, leaving the Army and Air Force. With the testing complete it was found that none of the rifles proved to be significantly more lethal or effective than the M16A2 they were pitted against. The program summary put a rather positive spin on the program’s failings, concluding that despite the increased hit probabilities not being attained as a technology base program, the ACR program was a success. The soldiers taking part in the field tests performed better than expected and “the baseline performance of the M16A2 rifle was better than anticipated in terms of hit probability.”
The report concluded that the program had helped push small arms technology forward, noting that while flechettes proved to be too inaccurate for an individual weapon,
“The feasibility of caseless and lightweight plastic-cased ammunition has more than been demonstrated in this program. Few problems were experienced with the [H&K] caseless rifles in the test. The past technical barriers of cook-off and vulnerability have now been overcome. …plastic cases cannot be used in conventional weapons like the M16A2, but with weapons specifically designed for it, complete plastic cases are feasible.”
This last observation is something that is again now being developed in the Lightweight Small Arms Technologies (LSAT) program, which has now been linked with the US Army’s current Next Generation Squad Weapon program.
With the end of the ACR program the school of thought moved towards the use of high explosive and airburst munitions by individual soldiers. The Objective Individual Combat Weapon program ran throughout the early 1990s and while it lead to the adoption of some new weapons, such as the M320 grenade launcher, it also failed in its goal to create an integrated individual weapon system.
If you enjoyed the video and this article please consider supporting our work here.
Bibliography:
Advanced Combat Rifle, Program Summary, Vol.1, ARDEC, 1992 (source)
‘Revisiting the SPIW Pt.3’, Small Arms Review, R. Blake Stevens, (source)
Our thanks to the collection that holds these wonderful examples of the ACR rifles
The Armourers Bench 
