5.56 NATO

Bushmaster

Bushmaster Bravo Zulu 5.56 NATO 16-inch Upper Receiver with M-LOK Handguard

Daniel Defense

Daniel Defense MK12 SPR URG 5.56 NATO Upper Receiver with 18-Inch Barrel

Daniel Defense

Daniel Defense DDM4 V7 URG 5.56 NATO Upper Receiver with 16-Inch Barrel

Daniel Defense

Daniel Defense MK18 RIII URG 5.56mm Upper Receiver with 9.5-inch M-LOK Rail in Matte Black