HK MR556 A4 5.56 NATO 11-Inch Threaded Barrel

The Heckler & Koch MR556 A4 is a semi-automatic firearm chambered for .223 Remington/5.56 NATO. It combines a short-stroke gas piston system with an adjustable gas regulator, an 11-inch threaded barrel, and fully ambidextrous controls.

This black configuration includes an M-LOK handguard, optics-ready receiver, black polymer grip, and one 10-round magazine. The threaded barrel uses a 1/2×28 pattern.

Key Specifications

• The chambering is .223 Remington/5.56 NATO.
• The operating system is a short-stroke gas piston design.
• The barrel measures 11 inches and features a threaded profile.
• The barrel has a 1-in-7-inch right-hand twist with six lands and grooves.
• The barrel thread pattern is 1/2×28.
• The firearm has fully ambidextrous controls and an ambidextrous safety lever.
• The handguard uses an M-LOK mounting interface.
• The receiver is optics ready and includes a black Picatinny rail.
• The overall length is 26.5 inches, and the listed weight is 6.61 pounds.
• The package includes one 10-round magazine.

With its compact barrel, piston-driven operating system, modular handguard, and ambidextrous controls, the MR556 A4 provides a carefully configured platform for range use and practical shooting applications. Its threaded barrel and optics-ready receiver support a range of compatible accessories while retaining the durable, functional design associated with the HK MR series.

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