The Weapon Collective share their first impressions of the MR556 A4 from Heckler & Koch. The MR556 A4, a commercial variant of the HK416, features a 5.56x45mm short-stroke gas piston system designed to reduce fouling and wear, with an adjustable gas regulator for suppressed or unsuppressed use. It includes ambidextrous controls, a lighter weight, and a slimmer profile, marketed as a high-reliability and durable AR-style rifle.