Question: The Ckm wz. 30 was a Polish-made clone of what American heavy machine gun used by the United States in World War I, World War II, Korea and to a limited extent in Vietnam?

full_context: Document 1: Machine gun: A machine gun is a fully automatic mounted or portable firearm designed to fire bullets in quick succession from an ammunition belt or magazine, typically at a rate of 300 to 1800 rounds per minute. Not all fully automatic firearms are machine guns. Submachine guns, rifles, assault rifles, shotguns, pistols or cannons may be capable of fully automatic fire, but are not designed for sustained fire. As a class of military rapid-fire guns, machine guns are fully automatic weapons designed to be used as support weapons and generally used when attached to a mount or fired from the ground on a bipod or tripod. Many (but not all) machine guns also use belt feeding and open bolt operation, features not normally found on rifles.
Document 2: Type 97 heavy tank machine gun: The Type 97 heavy tank machine gun (九七式車載重機関銃 , Kyū-nana-shiki shasai jū-kikanjū ) was the standard machine gun used in tanks and armored vehicles of the Imperial Japanese Army during World War II, a heavy machine gun by infantry forces, This weapon was not related to the Type 97 aircraft machine gun used in several Japanese Navy aircraft including the A6M Zero.
Document 3: Karabin maszynowy obserwatora wz.37: The karabin maszynowy obserwatora wz.37 (Polish for "observers machine gun") is a Polish version of the Browning wz.1928. It was a flexible machine gun used in the some Polish airplanes in the beginning of World War II.
Document 4: MCEM 2 submachine gun: MCEM-2 (Machine Carbine Experimental Model 2) submachine gun was produced only in prototype form, but was one of the very first submachine guns to combine wrap-around bolt and magazine in pistol grip, features later copied in the Czechoslovak Sa vz. 23, Israeli Uzi and a great number of other submachine guns. MCEM-2 was the second prototype in a line of experimental submachine guns, designed in Britain in 1944. It was envisioned as a possible replacement for the STEN submachine gun then in service. The MCEM-2 was developed by Jerzy Podsedkowski, a Polish constructor involved in work on Vis and Mors, who fled from occupied Poland to Britain. It is believed that prototypes of MCEM-2 were made before the end of WW2, and its derivatives MCEM-4 and MCEM-6 were tested soon after the war. The latter modifications differed mostly in adoption of the rate-reducing mechanism, incorporated into trigger unit; the rate of fire therefore was decreased from 1000 to more realistic 600 rounds per minute. Nevertheless, neither prototype was found suitable for adoption, and several years later British army adopted a more conventional submachine gun, the Sterling-Patchett.
Document 5: M1 link: The M1 link, was the U.S. military designation for a steel disintegrating link designed for the M1917 Browning machine gun and M1919 Browning machine gun, and the .30-06 Springfield cartridge that they fired. A single round would hold two links together, and more could be added to make up a belt of any quantity of rounds, though for the mounted machine guns of the time, a belt of 250 rounds was most commonly used. As was the trend with American belt-fed firearms, as opposed to Soviet designs, belts of ammunition feed into the gun from the left side to the right.
Document 6: Vickers machine gun: The Vickers machine gun or Vickers gun is a name primarily used to refer to the water-cooled .303 British (7.7 mm) machine gun produced by Vickers Limited, originally for the British Army. The machine gun typically required a six to eight-man team to operate: one fired, one fed the ammunition, the rest helped to carry the weapon, its ammunition, and spare parts. It was in service from before the First World War until the 1960s, with air-cooled versions of it on many Allied World War I fighter aircraft.
Document 7: Type 1 heavy machine gun: The Type 1 Heavy Machine Gun (一式重機関銃 , Iti-shiki juu-kikanjuu ) was a heavy machine gun used by the Imperial Japanese Army during the Second World War starting from 1941.
Document 8: Ckm wz. 30: Ckm wz. 30 (short for "ciężki karabin maszynowy wz. 30"; "heavy machine gun 1930 Pattern") is a Polish-made clone of the American Browning M1917 heavy machine gun. Produced with various modifications such as greater caliber, longer barrel and adjustable sighting device, it was an improved although unlicensed copy of its predecessor, and was the standard machine gun of the Polish Army since 1931.
Document 9: M2 Browning: The M2 Machine Gun or Browning .50 Caliber Machine Gun is a heavy machine gun designed toward the end of World War I by John Browning. Its design is similar to Browning's earlier M1919 Browning machine gun, which was chambered for the .30-06 cartridge. The M2 uses the much larger and much more powerful .50 BMG cartridge, which was developed alongside and takes its name from the gun itself (BMG standing for "Browning Machine Gun"). It has been referred to as "Ma Deuce", in reference to its M2 nomenclature. The design has had many specific designations; the official designation for the current infantry type is Browning Machine Gun, Cal. .50, M2, HB, Flexible. It is effective against infantry, unarmored or lightly armored vehicles and boats, light fortifications and low-flying aircraft. The M2 has been produced longer than any other machine gun.
Document 10: M1917 Browning machine gun: The M1917 Browning machine gun is a heavy machine gun used by the United States armed forces in World War I, World War II, Korea, and to a limited extent in Vietnam; it has also been used by other nations. It was a crew served, belt-fed, water-cooled machine gun that served alongside the much lighter air-cooled Browning M1919. It was used at the battalion level, and often mounted on vehicles (such as a jeep). There were two main iterations of it: the M1917, which was used in World War I; and the M1917A1; which was used thereafter. The M1917, which was used on some aircraft as well as in a ground role, had a cyclic rate of 450 rounds per minute; the M1917A1 had a cyclic rate of 450 to 600 rounds per minute.
Document 11: Hełm wz. 31: The hełm wz. 31 ("helmet, 1931 pattern") was the basic combat helmet of the Polish Army before the outbreak of World War II and during the Invasion of Poland. The helmet became the basic type of combat headgear for Polish military formations in 1930s and during the early stages of World War II. It was also exported to Persia, Albania and Republican Spain. By September 1939 approximately 320,000 copies were delivered to the Polish Army.
Document 12: Breda Model 1931 machine gun: The Breda Model 31 was a widely used Italian heavy machine gun produced by Società Italiana Ernesto Breda and used by the Italian Navy and Italian Army during World War II. At sea it was employed as a light anti-aircraft gun, while on land it was mounted on armored command vehicles where it was used as a heavy machine gun. After World War II it remained in use aboard the patrol boats of the Guardia di Finanza.
Document 13: Type 77 heavy machine gun: The Type 77 heavy machine gun is described as China’s first generation designed 12.7 mm heavy machine gun. The Type 85 is a “product improved” version. The weapon is both gas (three settings) and recoil operated. The ammunition belt is the standard DShK metal non-disintegrating link.
Document 14: M3 submachine gun: The M3 was an American .45-caliber submachine gun adopted for U.S. Army service on 12 December 1942, as the United States Submachine Gun, Cal. .45, M3. The M3 was chambered for the same .45 round fired by the Thompson submachine gun, but was cheaper to produce, and lighter, although, contrary to popular belief, it was far less accurate. This myth stems from a US army training film portraying the M3 as more accurate than its counterparts. The M3 was commonly referred to as the "Grease Gun" or simply "the Greaser," owing to its visual similarity to the mechanic's tool.
Document 15: M45 Quadmount: The M45 Quadmount (nicknamed the "meat chopper" and "Krautmower" for its high rate of fire) was a weapon mounting consisting of four of the "HB", or "heavy barrel" .50 caliber M2 Browning machine guns (of the M2 Turret Type (TT) variant) mounted in pairs on each side of an open, electrically powered turret. It was developed by the W. L. Maxson Corporation to replace the earlier M33 twin mount (also from Maxson). Although designed as an anti-aircraft weapon, it was also used against ground targets. Introduced in 1943 during World War II, it remained in US service as late as the Vietnam War.
ground_truth: The M1917 Browning machine gun