50 Caliber MK 211 Mod O Raufoss ammo. Lake city head stamp.
The multipurpose concept developed by Raufoss is unique in that, instead of using a mechanical fuse, it uses a pyrotechnical detonation train to ensure proper detonation of the explosive and incendiary components.[
The Mk 211 is a very popular .50 caliber sniper round used in the Barrett M82 rifle and other .50 BMG rifles. It is also often used in heavy machine guns such as the M2 Browning. Due to its popularity, several U.S. arms manufacturers produce the round under license from NAMMO Raufoss.