This is Armscor .223 Remington 55-grain FMJ ammo.

ARMSCOR USA ammunition line is made in the USA. The company offers a wide selection of competitively priced ammunition and components with sales spread throughout the world. ARMSCOR, an ISO 9001 Certified Company, complies with the SAAMI, CIP and other military or customer desired standards or requirements. ARMSCOR cartridges and components are widely used by the police, military, gun hobbyists, combat shooters and other shooting enthusiasts due to its high quality, precise and dependable performance.