Heckler & Koch (H&K) MR556 A4 5.56 NATO Upper Receiver Kit - 16.5"

This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HK’s piston and pusher rod system. This system utilizes a piston and a pusher rod in place of the gas tube normally found in AR15/M16/M4-style rifles. This closed system virtually eliminates the malfunctions that are common in direct-impingement gas systems, since hot carbon fouling and waste gasses are not propelled into the receiver area to operate the action. This is the same key feature critical to the success of the HK416 used by elite military and law enforcement customers. Upper will ship in HK Soft case.

• Complete MR556 A4 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
• Adjustable Gas Block
• Ships in HK Soft case.