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.