Heckler & Koch MR556 A4 Upper Receiver Kit with 16.5-inch Barrel, Black

Heckler & Koch MR556 A4 Upper Receiver, 223 Remington/556NATO, 16.5 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 51000384

Upgrade your 5.56mm AR-style rifle with the Heckler & Koch MR556 A4 Upper Receiver Kit, featuring advanced A4 specifications and a 16.5-inch barrel designed for precision and reliability. This complete assembly includes a new barrel profile, adjustable gas block, and a handguard, offering enhanced performance and customization options. Designed to retrofit Mil-Spec rifles to HK's piston and pusher rod system, it provides a significant upgrade over traditional direct-impingement systems by virtually eliminating malfunctions caused by carbon fouling and waste gases. The piston system used in this kit is the same as the one employed in the renowned HK416, trusted by elite military and law enforcement units worldwide. Built in the USA with a combination of US and German components, this upper receiver ensures durability, accuracy, and compatibility with a wide range of quality 5.56mm or .223 ammunition. The compact design, featuring a shortened buffer and action spring, optimizes performance for rifles with collapsible or adjustable stocks, but requires Mil-Spec hammers for installation on non-HK lower receivers. Whether you're upgrading your current rifle or building a new one, this HK MR556 A4 upper receiver kit offers a dependable and precision-engineered solution for demanding shooters and professionals alike.

Features:

• Complete upper receiver and barrel assembly for easy installation

• Includes 16.5-inch barrel with optimized profile for accuracy

• Adjustable gas block for enhanced control and tuning

• HK piston and pusher rod system reduces malfunctions caused by fouling

• Compatible with Mil-Spec 5.56mm AR-style rifles and components

• Assembled in the USA using US and German-made parts for quality assurance

• Designed for reliability and precision in demanding conditions

• Black finish provides corrosion resistance and a sleek appearance

• Shortened buffer and action spring for improved performance in collapsible stocks

• Requires Mil-Spec hammer for installation on non-HK lower receivers