The BAR weighs about 20 pounds unloaded, and is fed with a 20-round detachable box magazine loaded from the bottom just behind the foregrip. The BAR could take standard .30-`06 Springfield ammunition, as well as Tracer and Armor-Piercing rounds.
When it was issued as the M1918A1 in the latter days of World War One, Soldiers were issued a "cup" that held the stock of the rifle up to the hip, so the user could lay down suppressing fire whilst moving. The M1918A1 also had Semi-Automatic fire.
In 1940, the M1918A2 was issued to troops that were yet to fight in combat. It removed Semi-Automatic fire in favor of a Rate of Fire selector switch, located on the trigger guard that allowed the user to go from 300-450 RPM (slow) and 500-650 RPM (fast). It also improved the stock using a buffer spring in the butt of the rifle. Also, the M1918A2 came with a bipod that weighed 2 pounds. Most soldiers discarded the bipod to reduce the weight they had to carry.
It served from the latter days of World War One, into World War Two and ultimately ended its service shortly before the Vietnam War.