M1918 BAR Machine Gun

The M1918 BAR (Browning Automatic Rifle) Machine Gun was one of the most crucial machine guns in the entirety of WWII. The M1918 is a part of the BAR series, created by a man named John Browning. The M1918 was an almost 10 kg rifle, which had a round capacity of 20 and could shoot at a rate of 550 rounds per minute. The M1918 was first conceived in 1917 (in the midst of WWI) and   was first used by the U.S army in 1918, but at this point the war was almost over, and as a result only 85 M1918s were built before the end of the war. The weapon's design was so popular that many European countries rushed to get a license to produce the M1918s such as Belgium and Poland. Both the Belgian and the Polish variants of the M1918 were extremely similar to the original model besides very minor differences like how both new variants were slightly shorter, and slightly heavier than the original model.
At the outbreak of the war when Poland was first attacked, the Germans managed to get there hands on the Polish variant of the M1918. The Germans stole these M1918s and made them their own by renaming them IMG 28. Back in America, the M1918 was being modified to have two different firing rates at 500-650 rounds per minute and the slower 300-450 rounds per minute. The M1918 was a candidate for the standard light machine gun in every squad, but the idea was never implemented as there were other light machine guns which fit that specific role better. All soldiers in the U.S army were trained to operate a M1918, and the consensus regarding the rifle was that it was reliable, but it was difficult to clean and often fell victim to corrosion.
The M1918 continued to see some use after WWII, for example it was used by the Americans in the Vietnam War, but its use was on the decline. The U.S continued to use the M1918 up until the mid 1970s and some nations continued to use it up until the 1990s.

Sources: https://ww2db.com/weapon.php?q=52