The K2 was created during the 1980s, to replace the older M16A1 rifles used by the South Korean Army since the 1970s. While being similar to the M16, only some parts are interchangeable.
The K2's forearm, grip, and stock is built of tough polymer. The stock is foldable. K2 uses the same magazines, fire control group, and bolt as the M16A1. The bolt carrier group is based off that of the M16, but the gas operating system is derived from the AK's long stroke gas piston system. The K2 will accept the Daewoo K201 grenade launcher, which is a grenade launcher derived from the American M203.
There have been upgrades and modernizations of the K2 in South Korean military service, including:
- A simple RAS that mounts on top of the receiver, with one on the top for optical sights, and one on the left to mount lasers and flashlights. Issued to MPs inside the DMZ (inter-Korean border) in conjunction with RDS, night-vision sights and sometimes, for guard-posts, with a simple bipod.
- A complete RAS/RIS with four rails, three short ones (sides and bottom) and a full-length rail on the top. Used by elite-units in conjunction with optical sights/RDS/EO-Techs, vertical fore-grip, NV-sights and sometimes with flashlights or AN-PEQ 2As.
- The K2C is a carbine variant of the K2, featuring a shorter 310mm/12in. barrel, the RAS mentioned above, and a 6-positions collapsible stock.
- The K2A is a modernized variant of the K2, it is currently being issued to special- and elite-forces throughout the South-Korean armed forces and will become the standard assault-rifle of the ROK-Army by 2015. It retains the full-length barrel, a 6-positions collapsible stock and a RAS.
All RAS/RIS mentioned above are of the MIL-STD-1913 Picatinny rail.