Heckler and Koch MR556 Upper Receiver Kit 16.5 Inch Barrel Free Floating Rail

The Heckler & Koch MR556 Upper Receiver Kit delivers a complete upper receiver and barrel assembly, bolt carrier assembly, buffer, and buffer spring that allows most high-quality 5.56 mm AR-style rifles to be retrofitted to HK's pusher rod system, delivering enhanced reliability and performance in a cohesive, drop-in package. This MR556 Upper Receiver/Barrel Assembly features a 16.5 inch cold-hammer forged barrel with forward assist and an extended convertible charging handle, paired with the HK Free Floating Rail System handguard for improved rigidity and accessory compatibility. The kit also includes the complete MR556 Bolt Group Assembly, ensuring a seamless fit and dependable cycling, while the tungsten-filled HK proprietary buffer and the HK proprietary buffer (action) spring work together to optimize recoil management and cycling reliability. Designed to integrate smoothly with HK's evolution toward precision and durability, this upper receiver kit enables enhanced accuracy, modularity, and upgrade potential for AR-style platforms, making it an ideal choice for operators, hunters, and enthusiasts seeking a sturdy, capable foundational component for an HK-inspired build.