Wikipedia:

The Browning Automatic Rifle (BAR) is a family of United States automatic rifles (or machine rifles) and light machine guns used by the United States and numerous other countries during the 20th century. It can be considered the first US "Assault Rifle" (aka a first generation assault weapon).[1] The primary variant of the BAR series was the M1918, chambered for the .30-06 Springfield rifle cartridge and designed by John Browning in 1917 for the U.S. Expeditionary Corps in Europe as a replacement for the French-made Chauchat and M1909 Benét–Mercié machine guns.
The BAR was designed to be carried by infantrymen during an assault[1] or advance while supported by the sling over the shoulder or fired from the hip. This is a concept called "walking fire" — thought to be necessary for the individual soldier during trench warfare.[2] The BAR never entirely lived up to the designers hopes; being neither a rifle nor a machinegun.[3]

Specifications:

Operation
Air cooled, gas operated, magazine fed, shoulder type
M1918A1
selective fire (fully and semi-automatic)
M1918A2
fully automatic
Caliber
.30 (30-06)
Muzzle velocity
853.4 mps (2800 fps)
Capacity
20-round detachable box magazine
(1) Bandoleer (BAR belt): 12 magazines
(2) Magazine changeable in 2-4 seconds
(but averaged 6-8 seconds in combat)
Weight
8.33 kg (18.5 lbs)
Overall length
119.4 cm (47 in.)
Rate of fire
550 rounds per minute
Effective range
550m (600 yds)
Ammunition
(1) Ball M2; 150 gr bullet, 50 gr charge
(2) Tracer M25, M1: for designating targets and signalling
(3) Armor piercing M2 (black tip); 165gr/53gr
(4) Armor piercing incendiary: for lightly armored flammable targets

From: http://jamesdjulia.com/ James Julia Auction Site
http://milpas.cc/rifles/ZFiles/Korean War Weapons/Automatic Weapons/Browning Automatic Rifle.htm