Machine gun
A rapid-firing automatic gun, usually mounted, from which small-arms ammunition is discharged [Collins English Dictionary].
The machine gun is a small caliber automatic weapon capable of sustained rapid fire. Most machine guns are belt-fed weapons that fire from 500 to 1,000 rounds per minute and will continue to fire as long as the trigger is held back or until the supply of ammunition is exhausted. The machine gun was developed in the late 19th century and profoundly altered modern warfare's character.
Modern machine guns are classified into three groups. The light machine gun, also called the squad automatic weapon, is equipped with a bipod and is operated by one soldier; it usually has a box-type magazine and is chambered for the small-caliber, intermediate-power ammunition fired by the assault rifles of its military unit. The medium machine gun, or general-purpose machine gun, is belt-fed, mounted on a bipod or tripod, and fires full-power rifle ammunition. Through World War II the term “heavy machine gun” designated a water-cooled machine gun that was belt-fed, handled by a special squad of several soldiers, and mounted on a tripod. Since 1945 the term has designated an automatic weapon firing ammunition larger than that used in ordinary combat rifles; the most widely used caliber is .50 inch or 12.7 mm, although a Soviet heavy machine gun fired a 14.5-millimeter round [Encyclopedia Britannica].
Military unit. Encyclopedia Britannica. Retrieved from: https://www.britannica.com/topic/military-unit
Machine gun. Collins English Dictionary. Retrieved from: https://www.collinsdictionary.com/dictionary/english/machine-gun