- 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
- NOTE: The MR556A1 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.