rifling (K1: 1-in-12 twist; K2: 1-in-7.3 twist); and gas system (the K1 uses a direct impingement gas system, while the K2 uses a long stroke gas piston system). In addition, some parts are not interchangeable between the two weapons even though they can use the same cartridge (KM193 (.223 Remington) 5.56 caliber; the K2 can also utilize the K100 (SS109) 5.56 caliber round). Variants XB At least 6 versions (XB1 to XB6) of prototype were made. XB6: Selected design among the prototype. XB7: Further development of the XB6. XB7C: Final experimental prototype. Also known as XK2. K2 Mass-produced variant. DR-100: Semi-automatic 5.56×45mm NATO version for civilian market. DR-200: Semi-automatic .223 Remington version for civilian market. DR-300: Semi-automatic 7.62×39mm version for civilian market. K2C (C="Carbine"): Carbine version of K2 rifle with Picatinny rail, M4-type buttstock, barrel reduced to . Exports started in 2012. K2C CQB: A manufacturer-proposed variant of K2C for close quarters combat operations, which was first unveiled by the name "The New K2C-1" in the ADEX 2017, and later renamed as "K2C CQB" in the DX KOREA 2018. It has a barrel and has a firing range up to 500 meters with a Colt SCW-type buttstock, flip up sights, a horizontally modified magazine well angle, integrated picatinny rails and ambidextrous selector switches. K2C1 (C="Exterior design changed without performance improvements", by the South Korean Defense Specification) : New variant featuring a quad accessory rail, full-length 1913 Picatinny optics rail, an AR-15-style six position collapsing and a Magpul-based foldable stock. Comes in two barrel lengths, 305 mm (12 in) and 465 mm (18.3 in). It was officially sent into production in March 2016 with first deliveries in June 2016. Users : K2C used by Special Forces Command (Cambodia) 128 K2s transferred according to a 2019 SIPRI small arms report. : Purchased in 2011. : Purchased in the late 1980s. : 210 K2 rifles purchased in 2008 and 2011. 806 K2s transferred according to a 2019 SIPRI small arms report. : K2C used by Iraqi special operations forces Golden Division (formerly Golden Brigade). : A standard-issue rifle of the ROK Armed Forces since 1985. Used extensively by the South Korean contingent in Operation Enduring Freedom and the Iraq War. A small number of K2Cs were tested by the Republic of Korea Army Special Warfare Command in 2014, but it has not been adopted by ROK forces. Later, tens of thousands of K2C1s