XM8 Lightweight Carbine
5.56mm Modular Assault Weapon System

Program History

In September 2002, the US Army's Project Manager for Soldier Weapons issued an urgent requirement for the development of a lightweight carbine, to be designated as the XM8. The US Army's Objective Individual Combat Weapon (OICW) contract was subsequently modified to include this weapon. Approval had already been granted in September 2001 to the development of a lightweight weapon family, which became referred to as the Modular Assault Weapon System. The prime candidate for the XM8 contract was derived from the kinetic energy component of the OICW. The XM8 would later become the basis for the proposed Modular Assault Weapon System, OICW's Increment 1.

In October 2002, Alliant Techsystems (ATK) was awarded a $5 million contract modification from the US Army Armament Research, Development, and Engineering Center (ARDEC), Picatinny, New Jersey, to the OICW contract the company had already recieved. The modification was to further develop the new XM8 Lightweight Assault Rifle. ATK Integrated Defense of Plymouth, Minnesota, and teammate Heckler and Koch of Oberndorf, Germany, would support the rapid development program, which investigated the potential of the XM8 as the lightweight assault rifle for the Army's Objective Force, as outlined in 2001. In November 2002, it is determined that no specific requirement for the XM8 or its associated family of weapons actually exists, and subsequently the OICW Program Office works with ATK and HK to determine the weapon's basic specifications.

The XM8 was part of the Army's effort to perfect an over-and-under style weapon, known as the XM29, also being developed by Alliant Techsystems and Heckler and Koch as part of the OICW program. That weapon fired special air-bursting projectiles and standard 5.56mm ammunition. However, after 3 generations of test weapons, the XM29 was still too heavy and unwieldy for Army requirements. Instead of scrapping the XM29, the Army decided to perfect each of XM29's components separately, so soldiers could take advantage of new technology sooner. The parts would be brought back together when lighter materials became available. The XM8 was to be the basis for the development of the 5.56mm component as part of the OICW's Increment 1 development. The air-burst weapon was Increment 2, while the complete system was Increment 3.

An early 2003 strategy change at the Program Executive Office, Soldier sped up the development of a potential replacement of the Army's assault weapons. They moved from an "evolutionary approach" to "spiral development." Under the evolution strategy, developers planned to build a complete system, then improve on it. The first built would be about an 80 percent solution. The second about 90 percent and the third would be 100 percent. That approach was seen as taking too long to get new technology in the soldiers' hands. Under the spiral approach, the team broke the system into subsystems. This allowed the parts to mature individually before being integrated into a single system. The final decision to split the 2 component parts of the OICW in separate elements came in 2004 with the decision to change from 20mm to 25mm ammunition in the air-bursting weapon component.

During a visit to Germany between 20 and 23 October 2003, weapons experts said they were impressed after watching Heckler and Koch engineers fire 4 high-capacity magazines, with 100 rounds apiece, in less than 5 minutes from their XM8 entrant.

The first 30 XM8 prototypes had been delivered as of November 2003, and entered testing, as part of what was then seen as a response to an urgent need. From December 2003 through late May 2004, soldiers got a chance to fire the prototypes in desert, tropical and arctic environments. A limited-user test then was conducted, possibly at Fort Campbell, Kentucky, where soldiers tested the prototypes for about 3 weeks while training in offensive and defensive scenarios. Problems identified in testing were low 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.

The Army ordered 200 XM8's for the Army Test and Evaluation Command to test during the last quarter of 2004. Improvements were to be made based on soldier and test feedback before the final 3 months of operational tests, which began in fall 2004. The final decision would be up to the Army's senior leadership, but in early 2004 weapons officials said they were confident the XM8 weapon system would be adopted. If all went well, the XM8 would be ready for fielding by late summer 2005.

The XM8 had performance better than or equal to the M4, offers increased reliability, was configurable to meet mission requirements by easy barrel change-out, and integrated sighting and pointing/illuminating devices. Lethality modules included a 40mm grenade launcher, as well as a 12-gauge shotgun module. The 40mm grenade launcher, designated the XM320, could be used in a stand alone mode or as a separable under-barrel module with the M16 rifle, the M4 carbine, or the XM8 carbine. The shotgun module was also used under-barrel on the M4, M16, or XM8. Both modules were under development as SEP Programs.

In 2004, Congress denied $26 million dollars funding for 7,000 rifles for a test fielding of the XM8 in 2005. The battery life had been extended, and a more heat-resistant plastic hand-guard added. However, the rifle still had goals that were unmet, primarily associated with the weapon's weight. The earliest product brochure listed the target weight for the carbine variant at 5.7 pounds (2.6 kilograms) with the then current prototype at 6.2 pounds (2.8 kilograms). The weight of the carbine prototype subsequently grew to 7.5 pounds (3.4 kilograms) according to a brochure released by Heckler and Koch and General Dynamics in January 2005.

During 2004, the Army also came under pressure from other arms makers to open up the XM8 to competition. Their main arguments was that the weapon being adopted was substantially different from the original XM29 competition that ATK and Heckler and Koch had actually won. In addition, the Army had a legislative obligation to give preference to US-based manufacturers, and also had an agreement with Colt Defense that required the Army to involve Colt in certain small-arms programs. Following complaints about the non-competitive procurement of the XM8 system originating both in Congress and from Colt, in November 2004 the Army reopened the bidding for the 5.56mm Modular Weapon System Family contract to other companies, modifying the contract in the process to include a system of weapons with 4 total variants: carbine, special compact, designated marksman, and light machine gun/automatic rifle.

Around the same time period, the US Special Operations Command began development of their own replacement for the M4 carbine. As early as 2002, SOCOM had identified an urgent requirement to provide an improved lightweight carbine. Initial development of what was termed the Enhaned Carbine was placed under the purview of the Special Operations Peculiar Modification (SOPMOD) Accessory Kit program. By 2004, the Enhanced Carbine had been split off into a separate program known as the Special Operations Forces Combat Rifle (SCR). Though both the US Army and SOCOM initially expressed an interest in combining efforts on the XM8, delays and other issues with the program led to a decision to select a different system. In November 2004, SOCOM awarded a contract for what had become the Special Operations Forces Combat Assault Rifle (SCAR) to FNH USA, a US subsidiary of FN Herstal in Belgium.

On 19 July 2005, the Army suspended the Request for Proposal (RFP) OICW Increment 1 program to review the requirements for the effort to replace existing M16 rifles and M4 carbines. The requirements would be rescoped as a Joint Services effort. The Army's proposal had received interest from the other military services, and was further supported by several internal reviews reinforcing the increase in the potential for joint use.

Congressional notification was made and the suspension of the program allowed joint requirements to be viewed and incorporated through the Joint Capability and Integration and Development System process, which began immediately. The original solicitation started on 11 May 2005, and was temporarily suspended effective 19 July 2005, until the Joint Requirements Oversight Committee (JROC) convened, which was scheduled for early September 2005. Upon the JROC's completion, the committee would issue a memorandum, which incorporated any new joint OICW Increment 1 requirements. The RFP would be amended accordingly, and issued with a revised effective date for receipt of proposals.

On 31 October 2005, the XM8 program was formally suspended, pending further US Army reevaluations of its priorities for small caliber weapons, and to incorporate emerging requirements identified during Operation Enduring Freedom and Operation Iraqi Freedom. The Government would also incorporate studies looking into current capability gaps during said reevaluation.

In 2007, Army testing laboratories at Aberdeen Proving Ground, Maryland, subjected the M4 carbine and 3 other weapons to a severe environmental test called the "Carbine Extreme Dust Test." The lab environment allowed engineers to push the weapons beyond their technical limits to better inform and understand what was required for the most capable weapons on the current battlefield. At the time it was the third such test for the Army's carbine of choice, the M4. The other 3 weapons tested were the XM8, the Heckler and Koch 416, and the FN SCAR-L.

The Army noted all the weapons in the test performed well. The number of stoppages all the carbines exhibited was roughly one percent or less of the total rounds fired by each, meaning the weapons had over a 98 percent reliability rate under the unique conditions. Though the M4 performed exceptionally well, it came in fourth compared to the other 3 carbines in this particular extreme single-environment (dust as the only condition) testing.

The Army subsequently submitted a request for funds in the FY10 budget to examine potential replacements for the M4 carbine. Despite plans to field the XM8 carbine as a replacement, no such replacement had been adopted in the regular US Army by the end of 2009. In December 2010, it was reported that the US Army was preparing to begin the trials.

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