Heckler & Koch XM8

"XM8" redirects here. For the satellite radio station, see'80s on 8.For the American tank, seeM8 Armored Gun System.

TheHeckler & KochXM8is a lightweightassault riflesystem developed from the late 1990s to early 2000s. The rifle was designed by Germansmall armsmanufacturerHeckler & Koch(H&K), and shares design and engineering with theirG36 rifle.

XM8
An early version of the XM8
Type	Assault rifle Automatic rifle Light machine gun Sniper rifle/Designated marksman rifle Personal defense weapon
Place of origin	Germany United States
Service history
In service	2010–present
Used by	Royal Malaysian Navy
Production history
Designed	2002
Manufacturer	Heckler & Koch Alliant Technosystems
Produced	2003–present
Variants	Seevariants
Specifications
Mass	3.4 kg (7.5 lb)
Length	840 mm (33 in)
Barrellength	320 mm (12.5 in)
Cartridge	5.56×45mm NATO
Action	Gas-operated,rotating bolt
Rate of fire	750 rounds/min
Muzzle velocity	approx. 900 m/s (seevariants)
Effective firing range	500 m (550 yd)
Feed system	30-round detachablebox magazine,100-roundC-Mag drum magazine
Sights	ISM-V Unmagnifiedreflex sight(4x for DMR variant)

The XM8 design was originally part of theObjective Individual Combat Weapon program(OICW), which was developing a "smart"grenade launchersystem with an underslung carbine rifle. The system was unable to meet performance and weight requirements and was eventually canceled. In the aftermath, the two portions of the OICW were separated, resulting in the XM8 andXM25projects.

While the XM8 was being considered by theUnited States Armyas a potential standard infantry rifle, to replace theM4 carbine,this project was put on hold in April 2005, and wasformally canceledon October 31 of that year. The weapon was adopted by theRoyal Malaysian Navyfor itsPASKALspecial forces.

History

AU.S. Marine Corpsweapons instructor presents an XM8 Carbine during the Infantry Operations Chief Symposium in August 2005.

The U.S. Army's purpose in contracting for this prototype weapon was to provide replacement options for theM16 rifleafter theXM29program ran into problems.The goal was a weapon that was cheaper, lighter, and more effective than the M16 andM4series of weapons. The XM8 was not just one weapon but a system which could be reconfigured with appropriate parts to be any one of several variants from a short-barreled personal defense weapon to abipod-equipped support weapon. It also included an integrated optical sight and IR laser aiming module/illuminator.

The XM8 was based on the rifle module ofAlliant Techsystems'sXM29 OICWproject, of which the weapon mechanisms were the responsibility of H&K. Following the indefinite delay of theObjective Individual Combat Weapon program,the U.S. Army requested that the contractors design stand-alone weapons from the XM29's kinetic energy and high explosive modules.

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 was that the battery life was too low 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 handguard, 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 that 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 handguard added. The earliest product brochure lists the target weight for the carbine variant at 2.6 kg (5.7 lb) with the then current prototype at 2.8 kg (6.2 lb). The weight of the carbine prototype had since grown to 3.4 kg (7.5 lb) according to a brochure released by HK andGeneral Dynamicsin January 2005.

U.S. Army leaders test fire the compact set-up of the XM8 atFort Benning,Georgiain August 2004.

During the same period, the Army came under pressure from other arms makersto 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 (seeXM29). Other issues were that the army has a legislated obligation to prefer U.S.-based manufacturers, and that a previous agreement withColt Defenserequired the army to involve Colt in certain small-arms programs. The XM8 program was put on hold 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 theOICWIncrement 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 asquad automatic weapon(SAW) configuration. No XM8 prototypes have been shown that actually match the capabilities of theM249(e.g. fast barrel replacement, high sustainedrate 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.

Funding for theM320 grenade launcher,a single-shot under-barrel grenade launcher similar to theM203that was originally intended for the XM8, was approved. The launcher is heavier than the M203, but does offer some advantages, such as no need for special mounting hardware and loading from the side instead of the bottom, which enables use of longer-than-standard grenades. The XM320 was designed for use with the existing inventory of M16s and M4s and is also compatible with the XM8. It can also be used as a stand-alone weapon.

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. On October 31, 2005, the OICW Increment One RFP was cancelled.

In an article inJane's Defence Weekly,April 26, 2006 (Vol 43, page 30) it is stated 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".

General Dynamicswas involved in latter stages and H&K had plans to produce the rifle at a plant inGeorgia.H&K wasBritish-owned at the start of the project, but was later bought back by a group ofGermaninvestors. Engineering work was done at facilities in the United States and Germany.

Near cancellation

A prototype XM8 carbine - lacking PCAP device on the side rails. Also has the open 'duckbill' rather than 'birdcage' styleflash suppressor

The U.S. military's XM8 program was almost canceled in the autumn of 2005 after being suspended earlier that year, but was limited to the use of Marines. Had this program not been specified, the XM8 system may have faced competition from weapons such as from theFN SCAR,Bushmaster ACRandHK416.It was later altered and entered as a candidate for theSCARcompetition but was unsuccessful.

Further testing

In autumn 2007 the XM8 was compared to other firearms in a 'dust test'.The competition was based on two previous tests that were conducted in summer 2006 and summer 2007 before the latest test in the autumn of 2007. In the summer 2007 test, M16 rifles and M4 carbines recorded a total of 307 stoppages. In the autumn 2007 test, the XM8 recorded only 127 stoppages in 60,000 total rounds while the M4 carbine had 882.TheFN SCARhad 226 stoppages and theHK416had 233. The difference between the XM8, HK416, and FN SCAR was not statistically significant when correcting for the less reliableSTANAG magazine.However, the discrepancy of 575 stoppages between the summer and autumn 2007 tests of the M4 had officials looking into possible causes for the change such as different officials, seasons, and inadequate sample pool size but have stated that the conditions of the test were ostensibly the same.

Design

XM8 testing; One shooter is kneeling with an XM8 Carbine and aXM320(a 40 mmgrenade launcher) attached, while the other uses the XM8 sharpshooter (designated marksman) variant.

An XM8 compact carbine variant with buttcap attached, fired by a U.S. Army weapons tester.

The XM8 is aselective-fire5.56mmassault rifle,firing from a closed rotary bolt. Its design and functioning is similar to that of theHeckler & Koch G36assault rifle, of which it is a derivative.

Materials and weight

The materials used to build the XM8 are almost entirelycomposites,with the notable exception of the cold-hammer-forged steel barrel. Preliminary tests in desert and arctic conditions have shown the XM8 to be a rugged weapon, though some complaints arose concerning an unspecified mechanical issue and melting handguards due to overheating when firing full-auto.

Much of the expected cost and weight savings are from the weapon's electronic sight. The baseline XM8 carbine (with its integrated sight), for example, can be compared to an M4 carbine with a host of previous-generation electronic add-ons like theAN/PEQ-2,Aimpoint CompM2,Advanced Combat Optical Gunsight,and/or BUIS. Without the advantage of the next-generation combined electronics sight, the XM8 would be both heavier and more expensive than the firearms it was intended to replace.

Accessories

The XM8 abandoned the standardPicatinny railfor attachment of weapon accessories, in favor of a new standard referred to as PCAP (PicatinnyCombatAttachmentPoints), small oval holes on the forward grip. (A variant was designed with MIL-STD-1913 rails — XM8 R; and some early XM8 prototypes had rails.) PCAP is not backwards compatible with currently fielded attachments that use MIL-STD-1913 rails without using an adapter. The benefit of PCAP, however, is the precision of the accessory's connection with the body of the weapon; accessories utilizing Picatinny rails often need adjustment if they are removed and reattached. Additionally, most standard accessory functionality is built into the XM8. Where functionality was missing, it was anticipated that accessories would be redesigned to utilize PCAP. In the new OICW Increment One competition, the army has left the choice of attachment technology up to the manufacturer, with requirements built into the RFP as to the ability of sights to maintain their zero.

The M4 carbine barrel is 368 mm (14.5 in) and the XM8 barrel is 317 mm (12.5 in) but the rifles have the same overall length. Although a shorter barrel generally results in lower muzzle velocity,Polygonal riflingpartially compensates for the loss of velocity from a shorter barrel. An electronic round counter was proposed for the XM8. The system would have tracked the number of rounds fired and the date and time of each shot. The data would then be accessed wirelessly by a device like a PDA. Another benefit would be to monitor unauthorized weapon use or corroborate field reports. Other features included completely ambidextrous controls and an integrated red dot/3x optical zoomscope(later changed to a red dot/1x sight). However thedesignated marksmanconfiguration used a 3.5x magnification scope.

Variants

NavyPASKALoperators on standby during 57th National Day Parade Of Malaysia. Sailor at left holds an XM8.

H&K XM8 Carbine attached with H&K AG36 Underbarrel Grenade Launcher of Royal Malaysian Navy's special forces, PASKAL.

For much of its life, four different models were proposed: a compact PDW (personal defense weapon) with a 241 mm (9.5 in) barrel, a carbine with a 317 mm (12.5 in) barrel, a sniper and automatic rifle variant, both with 508 mm (20 in) barrels. In addition aLight machine gunwith a 100-round dual drumBeta C-Magis proposed. Accessories such asoptical sights,agrenade launcher,and abipodwere integrated using a new system which allows for precision attachment (so that, for example, scopes do not have to be readjusted each time they are attached). Like the M4 and M16, the XM8 was chambered for the standard5.56×45mm NATOround and was normally equipped with a 30-round plasticbox magazinealso used in theG36.Although, this meant that the magazine housing was not compatible with M4 and M16's metalSTANAG magazinewithout using an adaptor. A 100-round dual drumBeta C-Magstyle magazine could also be used.

One of the XM8's unique features was its modularity. In addition to attachments mentioned above, this modularity allowed for quick repairs, barrel length changes, and even caliber changes in the field. Along with its basic components, the XM8 would have complemented theXM29,with such features as identical accessory mounts.

The number and type of variants in the family varied over its lifetime, this overview with three main versions is based from a press release in the early 2000s.

• XM8 compact carbine: 229 mm (9 in) barrel, PDW configuration, collapsing stockor buttcap;muzzle velocity720 m/s (2,362 ft/s)
• XM8 carbine with XM320 grenade launcher: 317 mm (12.5 in) barrel; muzzle velocity 815 m/s (2,674 ft/s)
• Automatic rifle: 508 mm (20 in) barrel, with muzzle velocity 916 m/s (3,005 ft/s)
• Designated marksman rifle: 508 mm (20 in) barrel, integrated folding bipod, 4X sight, 30/100-round magazine; with muzzle velocity 916 m/s (3,005 ft/s)
• Light machine gun: heavy 508 mm (20 in) barrel with integrated folding bipod, rate of fire from 600-750 rounds/min

Usage

While the XM8 fell out of favor with the U.S. Armed Forces, Heckler & Koch sought to market the rifle globally. In the meantime, theMalaysian Armed Forcesexpressed interest in using the rifle and by 2007 openly stated its intention to purchase the XM8 rifle. By 2010, theRoyal Malaysian Navyspecial unitPASKALbegan using the XM8 along with other Heckler & Koch assault rifles including theHK416andG36.

See also

• Adaptive Combat Rifle,modular rifle system.
• AN-94
• Barrett REC7
• Beretta ARX160
• FN SCAR
• XM25 CDTE
• XM7

External links

• Picatinny article from 2004 about XM8 (.mil)
• Defense-Update.com article on XM8
• Global Security.org article about XM8
• HKsystems.com overview