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MR556 A4 16.5" Upper Receiver Kit
SKU#51000384

$2,299.00

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.
In Stock

  • 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.
  • NOTE: The MR556 A4 Upper Receiver Kit is not classified as a firearm and can be purchased without a Federal Firearms License ( FFL).

Not all HK webshop products are shippable to all U.S. states. Please check local laws and regulations before ordering. Heckler & Koch does not warrant that a person may legally purchase, possess, or carry specific items offered on this website according to federal, state, or local laws. A person placing an order for such items on this website warrants that he or she is an adult and is under no legal restrictions which would prohibit such person from ordering, owning, possessing, or transferring these items under applicable federal, state or local law.