H&K 235975A5 Complete Upper 223 Rem/5.56 NATO 16" 4140 Steel

This kit has been designed and manufactured to Heckler & Koch's exacting standards of excellence and is intended for use in, and with, MIL standard buffer tubes, as are provided with the HK MR556A1 rifle. Due to the precise nature of the components of this kit, they must be installed as a complete kit to ensure proper operation. The MR556A1 Upper Receiver Kit (URK) consists of an MR556A1 upper receiver/barrel assembly, complete bolt mechanism, and buffer and action (recoil) spring. The MR556A1 Upper Receiver Kit is designed to be fully interchangeable with most high quality AR-style firearms. MR556A1 upper receiver kits can be used to retrofit many non-HK AR systems by replacing the aforementioned components with MR556A1 URK components.