HK DISCONTINUED MR556-A1 Complete Upper Receiver Kit

Includes MR556A1 upper receiver/barrel assembly with 16.5 inch cold-hammer forged barrel, free floating rail system handguard, complete bolt carrier assembly, HK proprietary buffer, recoil spring and is designed to be fully interchangeable with most high quality AR-style firearms. Designed to function with 5.56x45mm ammunition and also cycles most quality .223 Remington ammunition. NOTE: This kit does not work with fixed stock AR-15 rifles.