It was used by the ARVN in Vietnam and by the US advisers. The link I got was a USMC form for weapons reporting. You would be surprised what exists in the armoury of the Regular Forces ,Reserve and National Guard troops around the country. Some units never get rid of weapons unless they have to.
link below shows an advisor shooting a BAR on a range with the a ARVN trooper.
http://en.wikipedia.org/wiki/Browning_Automatic_Rifle