XM8 rifle The XM8 was the U . S . military designation for a lightweight assault rifle system under development by the United States Army from the late 1990s to early 2000s . The rifle is designed by German small arms manufacturer Heckler & Koch ( H & K ) , and shares design and engineering with their G36 rifle . The XM8 design was originally part of the Objective Individual Combat Weapon program ( OICW ) , which was developing a " smart " grenade launcher system with an underslung carbon rifle as a backup weapon . The system was unable to meet performance and weight requirements and eventually canceled . In the aftermath , the two portions of the OICW were separated , resulting in the XM8 and MX29 projects . 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 . However , the weapon is now in service with Malaysian special forces and some private military companies . History . The U . S . Army ' s purpose in contracting for this prototype weapon was to provide replacement options for the M16 rifle after the XM29 program ran into problems . The Army ' s goal was a weapon that was cheaper , lighter , and more effective than the M16 and M4 Carbine series 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 a bipod - equipped support weapon . It also included an integrated optical sight and IR laser aiming module / illuminator . The XM8 was based on the rifle module of Alliant Techsystems ' s XM29 OICW project , of which the weapon mechanisms were the responsibility of H & K . Following the indefinite delay of the Objective 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 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 lbs ( 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 lbs ( 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 ( see 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 . Funding for the M320 grenade launcher , which is a single - shot under - barrel grenade launcher similar to the M203 that was originally intended for the XM8 , was approved . The launcher is actually heavier than the M203 , but does offer some advantages . 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 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 . " 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 . Near cancellation . 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 the FN SCAR , Bushmaster ACR and HK416 . It was later altered and entered as a candidate for the SCAR competition but was unsuccessful . Further testing . In the Fall of 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 Fall of 2007 . In the Summer 2007 test , M16 rifles and M4 carbines recorded a total of 307 stoppages . In the Fall 2007 test , the XM8 recorded only 127 stoppages in 60 , 000 total rounds while the M4 carbine had 882 . The FN SCAR had 226 stoppages and the HK416 had 233 . The difference between the XM8 , HK416 , and FN SCAR was not statistically significant when correcting for the less reliable STANAG magazine . However , the discrepancy of 575 stoppages between the Summer and Fall 2007 tests of the M4 had Army 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 . The XM8 is a selective fire 5 . 56mm assault rifle , firing from a closed rotary bolt . Its design and functioning is similar to that of the Heckler & Koch G36 assault rifle , of which it is a derivative . 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 . In contrast , the M16A2 needs to be cleaned often , and has a barrel life of approximately 7 , 000 – 8 , 000 rounds . Much of the expected cost and weight savings are from the weapon ' s electronic sight . The sight is much more than a 1 . 5x red dot sight , 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 , 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 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 . Accessories . 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 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 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 . Variants . For much of its life , four different models were proposed : a compact PDW ( personal defense weapon ) with a 9 . 5 - inch ( 241 mm ) barrel , a carbine with a 12 . 5 - inch ( 318 mm ) barrel , a sniper and automatic rifle variant , both with 20 - inch ( 508 mm ) 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 . Although , this magazine was not compatible with M4 and M16 ' s metal STANAG magazine . A 100 - round dual drum Beta C - Mag style 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 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 . 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 , the Malaysian Armed Forces expressed interest in using the rifle . In 2007 , TEMPUR , a Malaysian defense magazine focussing on military news , published an article stating the MAF ' s intention to purchase the XM8 rifle . By 2010 , the Royal Malaysian Navy special forces known as PASKAL have begun using the XM8 along with other Heckler & Koch assault rifles including HK416 and G36 , to reduce over - reliance on the M4A1 carbine .