The XM8 was a developmental U.S. military designation and project name for a lightweight modern assault rifle system that was under development by the United States Army from the late 1990s to early 2000s. The Army worked with the German 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. Although there were high hopes that the XM8 would become the Army's new standard infantry rifle, the project was put on hold in April 2005, and was formally canceled on October 31, 2005.
General Dynamics was involved in latter stages and H&K had plans to produce the rifle at a plant in Georgia. H&K was British-owned at the start of the project, but was later bought back by a group of German investors. Engineering work was done at facilities in the United States and Germany.
XM8 Variants
XM8 testing; One operator is kneeling with an XM8 Carbine and a XM320 (a 40 mm grenade launcher) attached, while the other uses the XM8 sharpshooter (designated marksman) variant.
For much of its life, four different models were proposed: a compact PDW (personal defense weapon) with a 9.5-inch (241mm) barrel, a carbine with a 12.5-inch (318mm) barrel, and sniper and automatic rifle variants with 20-inch (508mm) barrels. In addition, accessories such as optical sights, a grenade launcher, and a bipod were 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 standard 5.56 mm NATO round and was normally equipped with a 30-round plastic box magazine. However, this magazine was not compatible with M4 and M16's metal STANAG magazine. A 100-round dual drum Beta C-Mag style magazine would have been used, as well.
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 the XM29, 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.
An XM8 compact carbine variant with buttcap attached, fired by a US Army weapons tester.
XM8 Materials and Weight
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.
Much of the cost and weight savings, not all of which have actually been achieved in the current prototypes, are from the weapon's electronic sight. The sight is much more than a 1.5x red dot scope, including IR lasers and pointers as well. 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 the AN/PEQ-2, Aimpoint CompM2, ACOG, 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 is intended to replace. The XM320 grenade launcher, intended to be used with the current M4/M16 firearms as well as the XM8 family, includes feature enhancements.
PCAP and MIL-STD-1913
XM8 abandons the standard MIL-STD-1913, for attachment of weapon accessories, in favor of a new standard referred to as PCAP (Picatinny Combat Attachment Points), 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 MIL-STD-1913 rails often need adjustment if they are removed and reattached. Additionally, most standard accessory functionality is built-in to 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.
Other
The M4 carbine barrel is 14.5 inches (368 mm) and the XM8 barrel is 12.5 inches (318 mm) but the rifles have the same overall length. Although a shorter barrel generally results in lower muzzle velocity, Polygonal rifling partially compensates from 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 zoom scope (later changed to a red dot/1x sight). However the designated marksman configuration used a 3.5x magnification scope.
General Dynamics was involved in latter stages and H&K had plans to produce the rifle at a plant in Georgia. H&K was British-owned at the start of the project, but was later bought back by a group of German investors. Engineering work was done at facilities in the United States and Germany.
| XM8 | |
|---|---|
| Type | Assault rifle |
| Place of origin | United States Germany |
| Service history | |
| In service | Cancelled as of 2005 |
| Used by | None |
| Production history | |
| Designed | 2002 |
| Manufacturer | Heckler & Koch |
| Produced | 2003–2004 (prototypes only) |
| Specifications | |
| Cartridge | 5.56x45mm NATO |
| Action | Gas-operated, rotating bolt |
| Rate of fire | 750 rounds/min |
| Muzzle velocity | 920 m/s |
| Feed system | 30-round detachable box magazine, 100-round C-Mag drum magazine |
| Sights | Unmagnified reflex sight (4x for DMR variant) |
XM8 Variants
XM8 testing; One operator is kneeling with an XM8 Carbine and a XM320 (a 40 mm grenade launcher) attached, while the other uses the XM8 sharpshooter (designated marksman) variant.For much of its life, four different models were proposed: a compact PDW (personal defense weapon) with a 9.5-inch (241mm) barrel, a carbine with a 12.5-inch (318mm) barrel, and sniper and automatic rifle variants with 20-inch (508mm) barrels. In addition, accessories such as optical sights, a grenade launcher, and a bipod were 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 standard 5.56 mm NATO round and was normally equipped with a 30-round plastic box magazine. However, this magazine was not compatible with M4 and M16's metal STANAG magazine. A 100-round dual drum Beta C-Mag style magazine would have been used, as well.
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 the XM29, 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 Carbine with XM320 grenade launcher
- XM8 Compact Carbine: 9 in (229 mm) barrel, PDW configuration, folding stock or buttcap.
- Automatic Rifle / Designated Marksmen: heavy 20 in (508 mm) barrel, integrated folding bipod, 4X sight, 30/100 round magazine
An XM8 compact carbine variant with buttcap attached, fired by a US Army weapons tester.
XM8 Materials and Weight
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.
Much of the cost and weight savings, not all of which have actually been achieved in the current prototypes, are from the weapon's electronic sight. The sight is much more than a 1.5x red dot scope, including IR lasers and pointers as well. 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 the AN/PEQ-2, Aimpoint CompM2, ACOG, 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 is intended to replace. The XM320 grenade launcher, intended to be used with the current M4/M16 firearms as well as the XM8 family, includes feature enhancements.
PCAP and MIL-STD-1913
XM8 abandons the standard MIL-STD-1913, for attachment of weapon accessories, in favor of a new standard referred to as PCAP (Picatinny Combat Attachment Points), 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 MIL-STD-1913 rails often need adjustment if they are removed and reattached. Additionally, most standard accessory functionality is built-in to 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.
Other
The M4 carbine barrel is 14.5 inches (368 mm) and the XM8 barrel is 12.5 inches (318 mm) but the rifles have the same overall length. Although a shorter barrel generally results in lower muzzle velocity, Polygonal rifling partially compensates from 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 zoom scope (later changed to a red dot/1x sight). However the designated marksman configuration used a 3.5x magnification scope.
