The HK MR556 A4 is a semi-automatic 5.56mm rifle from Heckler & Koch USA, built in a California-compliant configuration around a 16.5-inch barrel (brand part no. 81001033). Classified as a rifle rather than a pistol or short-barreled configuration, it’s set up with a fixed 10+1 magazine capacity to meet state capacity restrictions. A 1-in-7-inch twist rate stabilizes a wide range of 5.56/.223 loads, and the rifle ships without factory sights, leaving the top rail ready for an optic of your choice. An ambidextrous selector-switch safety and semi-automatic action round out a rifle built to HK’s exacting manufacturing standards.

Key Specifications

• This rifle is classified as a Rifle product type, not a pistol or short-barreled configuration, for compliance purposes.
• It is chambered in .223 Remington/5.56 NATO.
• The 16.5-inch barrel is paired with a 1-in-7-inch twist rate.
• Capacity is set to 10+1, reflecting this rifle’s California-compliant configuration.
• It ships with one 10-round magazine.
• The rifle is finished in matte black.
• It ships without factory sights, leaving the top rail ready for an optic.
• A selector-switch safety provides ambidextrous control.
• It runs a semi-automatic action.

Frequently Asked Questions

Is the MR556 A4 legal in California? Yes, this configuration ships with a fixed 10+1 magazine capacity and other features to meet California’s compliance requirements.

Does it come with sights? No, it ships without factory sights, leaving the top rail ready for an optic.

What caliber does it use? .223 Remington/5.56 NATO.

Buy the HK MR556 A4 California-Compliant Rifle

Reserve the HK MR556 A4 from our Heckler & Koch lineup, and our Lubbock, Texas team will reach out as soon as it’s ready to ship, insured and sent to your local FFL. Compare it with other options in our rifle selection while you wait.