Heckler & Koch MR556A1 Upper Receiver Kit with 16.5" Barrel and 9" Handguard - HK 81000077

Complete MR556A1 upper receiver assembly kit featuring a 16.5" cold-hammer forged barrel, bolt carrier group, buffer, and buffer spring for retrofitting AR-style 5.56mm rifles to HK's pusher rod system. Includes HK Free Floating Rail System handguard and extended convertible charging handle with forward assist. Install requires field stripping the lower receiver and mating with compatible AR-15 lower.