H&K MR556A4 | 5.56 NATO | 11-inch | 10+1

The Heckler & Koch MR556A4 is an 11-inch, AR-style semi-automatic firearm chambered in .223 REM/5.56 NATO. It features a threaded barrel, an M-LOK handguard and a gray Cerakote finish, and ships with one 10-round magazine. The package emphasizes modular control and short-barrel maneuverability for range-focused shooting and competitive stages.

For optics, a compact red-dot such as the Aimpoint PRO offers durable, low-profile sighting that pairs well with this platform and remains under $1,000. Recommended applications include precision work on the range and competition-style shooting.

Product Specifications

• The manufacturer is HECKLER & KOCH INC..
• The model is MR556A4.
• The caliber is .223 REM/5.56 NATO.
• The barrel measures 11-inch for compact handling.
• The capacity is listed as 10 + 1.
• The overall length is 26.5 inches.
• The weight is 6.61 lbs..
• The action is Semi-Auto.
• The rate of twist is 1-in-7″.
• The finish is Gray Cerakote.
• The handguard is an M-LOK Handguard.
• The barrel is threaded (1/2×28).
• The package includes 1 10 rd. magazine.
• The lower receiver is Fully Ambidextrous Lower.
• The UPC is 642230272033.

This MR556A4 configuration brings H&K’s short-stroke gas piston design and a compact 11-inch profile to users who value a rugged, controllable platform for range training and competition. The M-LOK handguard and threaded barrel support accessory mounting and caliber-specific muzzle devices, while the ambidextrous lower improves ergonomics for a broad range of shooters. The MR556A4 is focused on mechanical reliability and modularity rather than unnecessary frills.