Caliber/Gauge
5.56x45mm
Barrel Length
16.5"
Color
Black
The MR556A1 Upper Receiver Kit includes a complete upper receiver/barrel assembly, bolt carrier assembly, buffer, and buffer spring allowing most high-quality 5.56 mm AR-style rifles to be retrofitted to HK's pusher rod system.
Complete MR556 Upper Receiver/Barrel Assembly HK 16.5 inch cold-hammer forged barrel, upper receiver with forward assist, extended convertible charging handle, HK Free Floating Rail System handguard
Complete MR556 Bolt Group Assembly
Tungsten Filled HK Proprietary Buffer
HK Proprietary Buffer (Action) Spring
Complete MR556 Upper Receiver/Barrel Assembly HK 16.5 inch cold-hammer forged barrel, upper receiver with forward assist, extended convertible charging handle, HK Free Floating Rail System handguard
Complete MR556 Bolt Group Assembly
Tungsten Filled HK Proprietary Buffer
HK Proprietary Buffer (Action) Spring
