Heckler & Koch MR556 A4 Upper Receiver, 223 Remington/5.56mm, 11" Barrel, Threaded 1/2X28, M-Lok Handguard, Anodized Finish, Black, Fits AR-15 Lower Receivers, Includes Bolt Carrier Group, Charging Handle, Buffer Weight and Buffer Spring

This kit includes a complete upper receiver/barrel assembly, allowing Mil-Spec 5.56mm AR-style rifles to be retrofitted to HKs 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.

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• Caliber : 5.56mm