XM8

The XM8 originated after the Objective Individual Combat Weapon programme was split into more manageable increments. Heckler & Koch developed it as a lightweight modular 5.56 mm weapon family for U.S. evaluation, drawing heavily on G36 operating principles while using a distinctive polymer-bodied external design. The programme generated prototypes but did not replace the M4.

The XM8 concept used a gas-operated 5.56x45 mm platform with interchangeable modules for carbine, compact, automatic-rifle, and marksman-style variants. Its polymer construction and integrated accessory approach were meant to reduce soldier load and simplify configuration changes. Mechanically, the system remained closer to proven HK rifle architecture than to the more complex combined-weapon XM29.

The U.S. Army evaluated the XM8 as a possible future individual weapon, but the programme was cancelled before broad procurement. Its influence continued through debates about modular rifles, polymer weapon construction, and alternatives to the M4. Limited foreign use, including Malaysian naval special operations reporting, kept the design from being purely experimental.