The innovative SHRIKE 5.56 upper receiver is designed to fit any MIL-SPEC quality AR-15/M16/M4-type lower receiver and features a dual-feed system, allowing users to configure the SHRIKE 5.56 from ...

An MR556A1 Upper Receiver Kit includes a complete barrel assembly ... The same operating system is used in the combat-proven 5.56 mm HK416 as well as the G36, XM8, HK417, and a variety of other ...