The XM8 assault rifle is a proposed replacement for the current M16 rifle and M4 carbine, the standard infantry weapons in today’s US military. The XM8 action is based upon the Heckler & Koch G36, a tried and true infantry weapon with a reputation for toughness and reliability.

The XM29 OICW project, which combined both an assault rifle and a smart grenade launcher, turned out to be too heavy, fragile, and expensive. The rifle part of the XM29 was adapted to become the XM8. The smart grenade launcher part of the XM29 is being developed separately as the XM25.

History

The XM8 is a developmental U.S. military designation and project name for a lightweight assault rifle system that was under development by the United States Army from the late 1990s to early 2000s. The Army worked with the small arms manufacturer Heckler & Koch (H&K) to develop the system to its requirements in the aftermath of the OICW contract, for which H&K had been a subcontractor to ATK (General Dynamics was involved in latter stages). Although there were high hopes that the XM8 would become the Army’s new standard infantry rifle, the project was put on hold in mid 2005, and was formally cancelled on October 31, 2005.

The first 30 XM8 prototypes were delivered by November 2003 for preliminary testing. Later, at least 200 developmental prototypes were procured. Among the complaints during testing were too low a battery life for the weapon’s powered sight system and some ergonomics issues. Two other key issues were reducing the weapon’s weight and increasing the heat resistance of the hand guard, which would start to melt after firing too many rounds.

The main testing was largely completed, and the Army pushed for funding for a large field test. However, in 2004 Congress denied $26 million funding for 7,000 rifles to do a wide scale test fielding of the XM8 in 2005. At the time the rifle still had developmental goals that were incomplete, primarily associated with the weapon’s weight; the battery life had been extended, and a more heat-resistant plastic hand-guard added. The earliest product brochure lists the target weight for the carbine variant at 5.7 lb (2.6 kg) with the then current prototype at 6.2 lb (2.8 kg). The weight of the carbine prototype had since grown to 7.5 lb (3.4 kg) according to a brochure released by HK and General Dynamics in January 2005.

During the same period, the Army came under pressure from other arms makers to open up the XM8 to competition. The main argument was that the weapon that was being adopted was a substantially different system than for the original competition that ATK and H&K had actually won (XM29). Other issues were that the Army has a legislated obligation to prefer U.S.-based manufacturers, and that a previous agreement with Colt Defense required the Army to involve Colt in certain small-arms programs. The XM8 program was put on hold by the Army in 2004. The exact reason why this happened is a matter of debate; some combination of the aforementioned technical issues, funding restrictions, and outside pressure being involved.

In 2005, the Army issued a formal Request for Proposals (RFP) for the OICW Increment One family of weapons. This RFP gave manufacturers six months to develop and deliver prototype weapons with requirements very similar to the XM8 capabilities, but with the addition of a squad automatic weapon (SAW) configuration. Currently, no XM8 prototypes have been shown that actually match the capabilities of the M249 (e.g. fast barrel replacement, high sustained rate of fire, belt feed). The OICW Increment One requirement for the SAW includes fast barrel replacement and high sustained rate of fire, but leaves the ammunition feed choice up to the manufacturer.

As of July 19, 2005, the OICW Increment One RFP was put on an eight-week hold, with an indication given that the program was being restructured as a joint procurement program including the Army and unnamed other branches. On October 31, 2005, the OICW Increment One RFP was canceled until further notice.

In an article in Jane’s Defence Weekly, April 26 2006 (Vol 43, page 30) we learn that “The US Army has again delayed the procurement of its future infantry weapons, this time for more than five years, and is working to field two interim guns in the meantime.”

Description and Specifications

The materials used to build the XM8 are almost entirely composites — with the notable exception of the cold hammer forged steel barrel. Preliminary tests in desert and Arctic conditions have shown XM8 to be a rugged weapon, though some complaints arose. It is reported to be capable of firing 15,000 rounds without cleaning or lubrication and up to 20,000 rounds before barrel replacement. The M16A2 needs to be cleaned often, and has a barrel life of approximately 7,000–8,000 rounds.

Internally, the XM8 uses a rotary locking bolt system that functions and fieldstrips like those used in the M16 rifle and M4 carbine. The bolt is powered by a unique gas operating system with a user-removable gas piston and pusher rod to operate the mechanism. Unlike the current M4 and M16 direct gas system with gas tube, the XM8 gas system does not introduce propellant gases and carbon back into the weapon’s receiver during firing.

While the XM8 was not exposed to battlefield conditions, it’s still a feat the current service rifle hasn’t come close to rivaling. During their Oct. 20-23 2003 trip to Germany, the weapons experts said they were impressed after watching Heckler & Koch engineers fire four high-capacity magazines, with 100 rounds apiece, in less than five minutes.

This improved reliability can be credited to differences in the XM8′s operating system from the one in the M16. For instance, a thin gas tube runs almost the entire length of the barrel in all of the M16 variants. When the weapon is fired, the gases travel back down the tube into the chamber and push the bolt back to eject the shell casing and chamber a new round. The XM8′s gas system instead is connected to a mechanical operating rod, which pushes back the bolt to eject the casing and chamber the new round each time the weapon is fired. So there’s no carbon residue constantly being blown back into the chamber, reducing the need to clean the weapon as often. You don’t get gases blowing back into the chamber that have contaminates in them. The XM8 also has a much tighter seal between the bolt and the ejection port, which should cut down on the amount of debris that can blow into the weapon when the ejection port’s dust cover is open.

Details

• Caliber: 5.56 mm
• Cartridge: 5.56 x 45 mm NATO
• Weight: 6.4 lbs | 2.8 kg empty
• Designed: 2002
• Produced: 2003 — 2004 (prototypes only)

Variants of XM8

The XM8 is a modular weapon that can be adapted to different roles fairly easily. It can use any of four barrel sizes: 9″, 12.5″, 20″, and heavy 20″.

The 12.5″ barrel is the standard set-up, and with the adjustable buttstock, makes the Baseline Carbine variant. With the stock fully extended, it is 33″ long, the same as an M4 (which has a 14.5″ barrel). It weighs in at about 6.4 lbs, with a goal of being reduced to 5.7 lbs. The M4 with comparable accessories weighs nearly 9 lbs. The picture above shows an XM320 side-loading detachable grenade launcher mounted.

The 9″ barrel makes the weapon a submachinegun-like personal defense weapon (called the Compact Carbine) that would be ideal for vehicle crews. Also, it seems to be that Special Forces types would find it useful for urban raiding missions and the like. With the buttcap (as pictured on the right, second from the top) it is less than 21″ long overall.

There are two versions of the 20″ barrel. There’s a standard weight match-grade unit for sharpshooter work and a heavy-duty machinegun unit with a folding bipod for use as a sustained fire automatic rifle.

See XM8 in action (YouTube video) »

Manufacturer

Heckler & Koch

Engineering work was done at facilities in the United States and Germany by H&K, General Dynamics and ATK.

[via Murdoc Online.com, GlobalSecurity.org & Wikipedia]

There are a selection of AR / M16 ammo types. The 5.56×45 at top and bottom, the 7.62×51 (.308) second from top, 6.8 SPR and 9mm below that. From a few feet away they look pretty much the same, as you look more closely the differences are apparent in the magazines. Their stocks are all much the same, except the SBR which is sporting the Vltor Clubfoot Mod Stock. There are some cool angled shots of this selection of AR15 / M16 carbines:

[Via kill a computer.com]

Related posts:

M16 – United States Assault Rifle
Colt M4 – Versatile Carbine

The M4 Carbine is a family of firearms tracing its lineage back to earlier carbine versions of the M16, all based on the original AR-15 made by ArmaLite. It is a shorter and lighter version of the M16A2 assault rifle, achieving 80% parts commonality with the M16A2. The M4 has selective fire options including semi-automatic and three-round burst (like the M16A2), while the M4A1 has a “full auto” option in place of the three-round burst.

Colt M4 Carbine is a versatile weapon system with proven combat utility and performance providing the operator with the confidence required to accomplish any mission. Featuring a 14.5 in. (37 cm) barrel it is designed for use wherever lightness, speed of action, mobility and fire power are required. It can be comfortably carried, yet be instantly available to provide the power, accuracy and range of a 5.56mm Rifle. Proven in military operations, it stands alone as a first-line weapon system. Colt M4 Carbine is today’s weapon of choice; the weapon of the 21st century soldier.

The Colt M4 carbine entered service with US Army in 1994. Basically it is a shortened M16A2 assault rifle with a telescopic buttstock. This carbine was intended as a substitute for submachine guns. It is used by airborne troops, special forces, tank crews, vehicle drivers etc.

Description and Specifications

The M4/M4A1 5.56 mm Carbine is a gas-operated, air-cooled, magazine-fed, selective fire, shoulder-fired weapon with a telescoping stock. A shortened variant of the M16A2 rifle with a 36 cm barrel, the M4 provides the individual soldier operating in close quarters the capability to engage targets at extended range with accurate, lethal fire. The original M4 Carbine has semi-automatic and three-round burst fire modes, while the M4A1 has “semi” and “full auto”, with no three-round burst.

The M4 Carbine is an extremely accurate and effective weapon under all practical field applications. It is a favorite with both first line infantry operations as well as special forces, unit commanders and vehicle crews. Available with a Safe/Semi/Full Auto 3-position selector the M4 Carbine is today?s weapon of choice.

The M4 Carbine features a redesigned 4-position sliding buttstock allowing it to adapt to soldiers of different sizes and physical characteristics as well as various firing positions or clothing variations. Almost all mechanical components are interchangeable with those of the M16 rifle, ensuring quality, commonality of parts and reduced maintenance costs.

The Carbine barrel is designed to accept the M203 Grenade Launcher which can easily be assembled to the carbine offering the user both point and area firing capabilities. Also, all US and NATO rifle grenades can be fired without any supplementary equipment.

The Close Quarters Battle Receiver (CQBR) is a replacement upper receiver for the M4A1 Carbine. The CQBR upgrades the M4 with a barrel 10.3 in (260 mm) long, the modern equivalent of the Colt Commando short-barrel M16 variants of the past.

A CQBR in comparison to a standard M4A1

The M4 and M16 are not ideally suited for all missions, so it was proposed that the modularity of the M16 series would allow a user to replace the upper receiver of an existing weapon with one more suitable to the task. One of two proposed special mission receivers that were planned for inclusion into the SOPMOD Block II kit, the CQBR has taken off on its own. Like the proposed Special Purpose Receiver, the Close Quarters Battle Receiver has been more or less taken on by the Naval Surface Warfare Center, Crane Division (often referred to as NSWC-Crane or just “Crane”) as its own project following the CQBR’s removal from the SOPMOD program. Just as the Special Purpose Receiver morphed into the Special Purpose Rifle, and was type-classified as Mk 12 Mod 0/1, the complete CQBR-equipped carbine has been type-classified as the Mk 18 Mod. 0.

The purpose of the CQBR remains to provide operators with a weapon of submachine gun size, but firing a rifle cartridge, for scenarios such as VIP protection, urban warfare, and other close quarters battle (CQB) situations. The CQBR is designed to provide improvement over previous AR-15/M16-type weapons in this category. The CQBR is usually issued as a complete weapon system, and not just an upper receiver. The CQBR was once only available to Naval Special Warfare units, but the Mk 18 Mod 0 has become general issue for Visit, Board, Search, and Seizure (VBSS) missions.

The short 10.3 in (262 mm) barrel length requires special modifications to reliably function. The gas port is opened from 0.062 to 0.070 in (0.16 to 0.18 mm). A one-piece McFarland gas ring replaces the three-piece gas ring set. The standard 4-coil extractor spring is replaced with a commercial off-the-shelf (COTS) 5-coil spring. An O-ring surrounds the extractor spring.

• Caliber: .223 Rem / 5.56 mm
• Cartridge: 5.56 x 45 mm NATO
• Weight: 5.9 lb / 2.68 kg empty
• Effective range: 660 yd / 600 m
• In service: 1994 – present

Manufacturer

Colt Firearms

Mission

Deter and, if necessary, compel adversaries by enabling individuals and small units to engage targets with accurate, lethal, direct fire.

History

The M14 was the U.S. Army’s original choice to replace World War II era M-1 and Browning Automatic rifles. The M14 was an unhappy compromise weapon, that satisfied virtually no one, least of all the men for whom it was intended. General dissatisfaction with the M14 and numerous studies led the Army to the development of a light weight weapon capable of firing a burst of small caliber bullets with a controlled dispersion pattern. Unfortunately, the M14′s follow-on initially fared little better.

M16

The replacement for the M14 was designed by Eugene Stoner, of the ArmaLite Company, as the AR-15 around 1956. The AR-10 was conceived by Eugene Stoner as a 7.62mm Basic infantry rifle in 1955. At that time the Army was considering replacements for the M1 Garand. The AR-10 was stunningly different than any previous design. It was produced with aircraft grade aluminum receivers, and therefore weighed less than seven pounds. The stock and other furniture were plastic, while the T-44 and T-48 were of wood. The configuration of the rifle itself, with its integral carrying handle and charging handle distinctively mounted within it, sparked intense curiosity. In the end, the AR-10 wasn’t able to catch up, and eventually lost out to the M14 rifle in 1959.

M16A1

Based on the AR-10, Army officials asked ArmaLite to develop a smaller version of the AR-10 in 1956. The ensuing rifle was called the AR-15. Army analysis of battlefield statistics from WWI, WWII and Korea, had shown that most kills from small arms occured at ranges of less than 300 yards. This suggested that the military should seriously consider lighter weight, higher capacity weapons. Seeking a novel cartridge suitable for a smaller caliber assault rifle, Eugene Stoner approached Winchester Corporation. The result was the small but powerful .223 (5.56 mm) rifle cartrdige — high-velocity, light weight, low recoil, and capable of penetrating a helmet per U.S. Army specifications.

Production of the AR-15 rifle was licensed to to Colt Manufacturing Company in 1959. Early Colt AR-15s, their magazines, and their operators manuals were marked with ArmaLite’s name. Colt’s retained the AR-15 designation on commercial rifles. To this day Colt’s has a model designation with the letters AR, which stands for “ArmaLite”.

The AR-15 was selectable for full and automatic fire. The AR-15 was to have had the same effective range as the M14 rifle, but it was most effective at a range of 215 yards (200m) or less. The M16 used a 5.56mm (.223 cal.) cartridge in 20- or 30-round magazines. To compensate for the reduced size of the 5.56 mm bullet, the AR-15 designers increased the velocity of the bullet so that it would have an adequate range and the flat trajectory needed for accurate aiming. The M16 bullet had a muzzle velocity (velocity on leaving the gun) of 980 meters per second as compared to 870 meters per second for the M14 rifle and 720 metres per second for the Soviet AK-47 7.62 mm rifle, while at a range of 100 meters the velocities of the three bullets were 830, 800, and 630 meters per second respectively.

The U.S. Air Force completed tests of the AR-15 in January 1961. The Air Force procured 8,500 rifles in 1961 and standardized the AR-15 in 1963. The weapon was first deployed to the Air Force’s Air Police. The original AR-15 was designated the M16 in 1962.

The new rifle had the advantage from a military point of view of weighing one- fourth less than the M14, and the ammunition also was lighter, reducing the recoil against the soldier’s shoulder and enabling a soldier to carry more rounds. As interest in the problems of counter-insurgency grew under the Kennedy administration in the early 1960s, the U.S. military quietly bought several thousand AR-15s and sent them to Vietnam for testing in combat conditions.

In the Vietnam era, DARPA (then ARPA) gained acceptance for the AR-15 by sponsoring its demonstration in combat. Colt brought the weapon to DARPA in 1962. Through Project AGILE, DARPA purchased 1,000 AR-15s and issued them to combat troops in Southeast Asia for field trials, to prove that the high-velocity 5.56 mm round had satisfactory performance. The subsequent DARPA report, documenting the lethality of the AR-15, was instrumental in motivating the Secretary of Defense to reconsider the Army’s decision and eventually adopt a modified AR-15 as the U.S. military individual weapon of choice. Although opposed by the Ordnance Corps, the Armalite AR-15 was adopted by the Secretary of Defense as the 5.56mm M16 rifle.

Soon reports began appearing of the lethality of the new rifle. Unofficial reports said the AR-15′s light bullet, travelling at 3,300 feet per second, did cartwheels as it penetrates living flesh, causing a highly lethal wound that looks like anything but a caliber .22 hole, the U.S. magazine Army reported in August 1963. Two U.S. Army doctors who evaluated AR-15 wounds at an Army hospital in South Vietnam in 1966 reported that while wounds inflicted at close range had small entrance and exit holes, those at larger ranges exhibited small entrance holes whereas the exit wound is a gaping, devastated area of soft tissue and even bone, often with loss of large amounts of tissue, with disintegration of the bullet and minute splattering of lead.

By 1963 U.S .Army was purchasing the M16 for use in South East Asia and by various elite forces. The Army also ordered 85,000 rifles in 1963. An additional 35,000 were ordered in 1964, 100,000 in 1965, and 100,000 in 1966. These rifles were initially issued primarily to combat troops in the Dominican Republic and to Special Forces, Airborne, helicopter crews, Air Commando and other special category troops in Vietnam.

The M16 was type classified standard A in 1965 and became the military’s basic service rifle. By 1966 it was in widespread use. The M16 was called the “black rifle” and “Mattel toy” thanks to its appearance. Troops liked the light weight, but complained about insufficient range and lethality. While the M16 had been marketed as virtually “maintenance free, poor maintenance instructions (or even no instructions) and jungle climate together with the fouling-prone direct gas system caused trouble. Its high rates of fire in the jungle environment had a larger impact on increasing American morale than on actually inflicting enemy casualties. The move to high-velocity 5.56 mm was also subsequently adopted by the Israelis, the Soviets, and NATO allies. DARPA’s most significant contribution to this program was its willingness to “think outside of the box” and try something new.

The AR-15 was redesignated by the U.S.Army as the M16 rifle, and in 1967 the Army announced that it would be adopted as the standard infantry weapon for U.S. Forces outside NATO. By 1978 the rifle had been exported to 21 countries and was being produced under licence in another three, with various other 5.56 mm rifles in production elsewhere.

Description and Specifications

A lightweight, air-cooled, gas-operated, magazine-fed rifle designed for either automatic or semi-automatic fire through use of a selector lever. There are four variants – the M-16A1/A2/A3/A4. The M-16A2 incorporates improvements in iron sight, pistol grip, stock and overall combat effectiveness.

Accuracy is enhanced by incorporating an improved muzzle compensator, three-round burst control, and a heavier barrel; and by using the heavier NATO-standard ammunition, which is also fired by the squad automatic weapon. The M-16A3 is identical to the M-16A2 but has a removable carrying handle that is mounted on a Picatinny Rail (for better mounting of optics) and is without burst control. The M-16A4 is identical to the M-16A2 except for the removable carrying handle and Picatinny rail.

• Caliber: .223 in / 5.56 mm
• Cartridge: 5.56 x 45 mm NATO / .223 Remington
• Weight: 8.8 lbs / 3.9 kg includes sling & one loaded magazine
• Range: 875 yd / 800 m for an area target | 600 yd / 550 m for a point target
• In service: 1964 — present

Manufacturers

Colt Manufacturing and Fabrique Nationale Manufacturing Inc.