The Browning Automatic Rifle (BAR) could fire single shots or fully automatic bursts. The mechanism worked by expanding gases from the exploding cartridge charge compressing a return spring by means of a piston, then the return spring carrying forward the piston, hammer link and bolt assembly, this cycle being automatic. The rifle was 3 ft 7 in. long and weighed 15 ¾ lbs. It was magazine fed, the magazine holding 20 rounds. Sights were adjustable for 200 to 1,600 yards. It fired .300 caliber ammunition. The maximum rate of fire was 550 rounds per minute.
The Browning issued to the Home Guard did not have any support for the use as a light machine gun, requiring that the weapon had to be rested on something or fired like a rifle. The BAR Group normally consisted of five to seven men (Gun squad leader, gunner, loader, loader, remainder riflemen). The gun was normally to be used to fire single rounds in order to: