Daewoo Precision Industries K2 Daewoo Precision Industries K2 assault rifle was developed by the Agency for Defense Development and manufactured by Daewoo Precision Industries . It is currently used as the standard service rifle of the Republic of Korea Armed Forces . Shoulder - fired and gas - operated containing long - stroke piston , the K2 is capable of firing both 5 . 56x45mm NATO and . 223 Remington ammunitions , but use of . 223 Remington will fail to achieve its full potential , decreasing its accuracy and effective range slightly . The K2 supplanted the M16A1 assault rifle for the Republic of Korea Armed Forces since its adoption in 1984 . Development . Although Daewoo Precision Industries K1 submachine gun entered service 3 years before the K2 , the development of the K2 assault rifle started many years earlier . Because the produce of the M16A1 ( Colt Model 603K ) under the license will eventually expire and Colt did not wish to continue the license , president Park Chung - hee , who strongly believed in self - reliance of national defense , ordered the engineers to develop the standard firearm for the Republic of Korea Armed Forces thinking that a firearm is the basic and the base of the defense industry . The engineers of the Agency for Defense Development began the project named XB rifle in 1972 , and finished the project in 1983 . Colt once sued for the design of the K2 assault rifle suspecting the design was copied from M16 . Colt lost the case , and Daewoo Precision Industries does not pay license fee for manufacturing the K2 . Design . A total of 6 kinds of prototypes were made during the development . Of the 6 designs , the XB6 was selected . Some parts of the XB6 resembled FN FNC such as suppressor and sight . Further development of the XB6 evolved into the XB7 and finally the XB7C , also known as the XK2 . The K2 uses a tough polymer for the forearm , pistol - grip and side - foldable buttstock . Externally similar in appearance to the AR18 , its bolt carrier group is derived from the American M16 rifle , but only some of the parts are interchangeable . The gas operating system is derived from the AK - 47 , and is consequently different from that of the M16 . The K2 uses the same magazine as the M16 ; the bolt and bolt carrier does not interchange with the M16 . The fire control system is derived from that of the M16 but few parts interchange without modification . The barrel rifling has 6 grooves , 1 - in - 7 . 3 right hand twist . The K2 has 4 kinds of selective firing mechanism : safe , semi - auto , 3 - round burst , and automatic . The K2 can be equipped with the Daewoo Precision Industries K201 , an undercarried 40x46mm single shot grenade launcher patterned after the American M203 . The Republic of Korea Armed Forces originally planned to replace the entire K2 with new S & T Daewoo K11 dual - barrel air - burst weapon . However , due to extremely high cost and skepticism on firepower of 20mm grenade led to the decision to provide 2 K11s to each squad , keeping 2 grenadiers as well . The current 9 - infantry squad of the Republic of Korea Armed Forces is armed with 2 K2 rifles , 2 K2 rifles with K201 grenade launcher , 2 K11 DAWs , 1 K3 light machine gun , and the rest with either K1 or K2 . K1 submachine gun and K2 rifle . While the K1 / K1A submachine gun is commonly regarded as a carbine version of the K2 , the K1 a separate submachine gun altogether , as :