In 1965, the U.S. Army and U.S. Marine Corps' primary machine guns were the M2 Browning and M60. The M2 was a large-caliber heavy machine gun, usually mounted on vehicles or in fixed emplacements.[9] The M60 was a more mobile general-purpose machine gun intended to be carried by troops to provide heavy automatic fire.[10]

Both firearms were very heavy and usually required a crew of at least two in order to operate efficiently.[11] The Browning automatic rifle (BAR), the army's main individual machine gun since its introduction in World War I, was phased out in 1957 with the introduction of the M14 rifle (which had a fully automatic mode.)[12] Designated riflemen in every squad were ordered to use their weapons on the fully automatic setting, while other troops were required to use their rifle's semi-automatic mode on most occasions to increase accuracy and conserve ammunition.[13] Because the M14 and M16 were not designed with sustained automatic fire in mind, they often overheated or jammed.[13] The 20-round and 30-round magazines of these weapons limited their sustained automatic effectiveness when compared to belt-fed weapons.[9]