Question: The K2 is capable of firing a rimless bottlenecked intermediate cartridge derived from what cartridge?

Context paragraphs:
.505 Gibbs: The .505 Gibbs cartridge was designed by George Gibbs in 1911.  The cartridge was originally known as the .505 Rimless Nitro Express or simply as the .505 Rimless.  C.I.P. refers to the cartridge as the 505 Mag.  Gibbs in their publications.  It is a .50 caliber (12.8 mm) rimless bottlenecked cartridge intended for magazine-fed rifles.

5.56×45mm NATO: The 5.56×45mm NATO (official NATO nomenclature 5.56 NATO) is a rimless bottlenecked intermediate cartridge family developed in Belgium by FN Herstal.  It consists of the SS109, SS110, and SS111 cartridges.  Under STANAG 4172, it is a standard cartridge for NATO forces as well as many non-NATO countries.  It is derived from, but is not identical to, the .223 Remington cartridge.

5.8×42mm: The 5.8×42mm / DBP87 ("Dàn (弹) Bùqiāng (步枪) Pŭtòng (普通), 1987"; literally "Standard Rifle Cartridge, 1987") is a military rimless bottlenecked intermediate cartridge developed in the People's Republic of China.  There is limited information on this cartridge, although the People's Liberation Army says that it is superior to the 5.56×45mm NATO and 5.45×39mm Soviet cartridges.  Another variant called the DBP88 “heavy round” was designed specifically for squad automatic weapons and designated marksman rifles.  The 5.8×42mm “heavy round” cartridge has the same dimensions as the standard 5.8×42mm cartridge, but utilizes a longer streamlined bullet with a heavy steel core for increased performance at extended ranges and penetration.  As of 2010 all 5.8×42mm cartridge variants are gradually succeeded by the DBP10 variant.

6×45mm SAW: The 6×45mm SAW describes an experimental series of rimless bottlenecked intermediate cartridges developed in the 1970s for the U.S. Army.  The cartridges were produced in a variety of sizes and from a variety of materials.  The intent was to develop a cartridge that would replace all 5.56×45mm NATO weapons as well as most 7.62×51mm NATO rifles and machine guns in the U.S. military.  Eventually, the 5.56mm was retained and only the machine gun portion of the SAW (Squad Automatic Weapon) competition was successful.  That program led to the M249 light machine gun.

7.92×33mm Kurz: The 7.92×33mm "Kurz (designated as the 7.92 x 33 kurz by the C.I.P.) is a rimless bottlenecked intermediate rifle cartridge developed in Nazi Germany prior to and during World War II.  The ammunition is also referred to as 7.9mm "Kurz ("German: "Kurz" " meaning "short"), 7.9 "Kurz", or 7.9mmK, or 8×33 Polte.  It was specifically intended for development of an automatic carbine (assault rifle).  The round was developed as a compromise between the longer 7.92×57mm rifle and the 9×19mm Parabellum pistol rounds, and is known as an intermediate cartridge (German: "Mittelpatrone" ).

6.8mm Remington SPC: The 6.8 mm Remington Special Purpose Cartridge (6.8 SPC, 6.8 SPC II or 6.8×43mm) is a rimless bottlenecked intermediate rifle cartridge that was developed by Remington Arms in collaboration with members of the U.S. Army Marksmanship Unit, United States Special Operations Command to possibly replace the 5.56 NATO cartridge in a Short Barreled Rifle(SBR)/Carbine.

Daewoo Precision Industries K2: Daewoo Precision Industries K2 assault rifle was developed by the South Korean Agency for Defense Development and manufactured by S&T Motiv (formerly Daewoo Precision Industries).  It is currently the standard service rifle of the Republic of Korea Armed Forces.  Shoulder-fired and gas-operated, the K2 is capable of firing both 5.56×45mm NATO and .223 Remington ammunition.  The K2 supplanted the M16A1 assault rifle for the Republic of Korea Armed Forces since its adoption in 1984.

5.45×39mm: The 5.45×39mm cartridge is a rimless bottlenecked Intermediate cartridge.  It was introduced into service in 1974 by the Soviet Union for use with the new AK-74 assault rifle.  The 5.45×39mm gradually supplemented, then largely replaced the 7.62×39mm cartridge in Soviet and Warsaw Pact service as their primary military service rifle cartridge.

7.62×39mm: The 7.62×39mm (aka 7.62 Soviet) round is a rimless bottlenecked intermediate cartridge of Soviet origin that was designed during World War II.  Due to the worldwide proliferation of RPD and RPK light machine guns and SKS and AK-47 pattern rifles, the cartridge is used by both militaries and civilians alike.  7.62×39mm ammunition is purportedly tested to function well in temperatures ranging from -50 to cementing its usefulness in cold polar or hot desert conditions.

7.62×45mm: The 7.62×45mm (designated as the 7,62 × 45 by the C.I.P.) is a rimless bottlenecked intermediate rifle cartridge developed in Czechoslovakia.  It is fired by the Czech vz.  52 rifle, Vz.  52 machine gun and ZB-530 light machine gun.  The round was later dropped from use when the Czech converted to the standard Warsaw Pact round, the 7.62×39mm (fired by vz.  52/57 rifle and vz.  52/57 light machine gun).  Its muzzle velocity and muzzle energy are slightly higher than that of the 7.62×39mm cartridge.

Supporting paragraphs: Daewoo Precision Industries K2 5.56×45mm NATO
Answer: .223 Remington