CMMG 55BB40BMB Resolute MK4 5.56 NATO 16.1" Rifle

The CMMG Resolute MK4 5.56x45mm NATO rifle with 16.10" barrel and midnight bronze finish delivers precision and modularity in a compact platform designed for tactical shooters and professional operators. This AR-platform rifle combines a free-float M-LOK handguard with a proven 5.56 NATO chambering, optimizing both accuracy potential and accessory flexibility. The upper receiver configuration ships without bolt carrier group or charging handle, allowing end users to select components matched to their specific mission requirements.

The 16.10" barrel length represents a practical balance in 5.56x45mm NATO rifle design—short enough for vehicle operations, building clearance, and CQB training environments, yet long enough to develop full cartridge velocity for duty-distance engagements. A free-float handguard isolates the barrel from support-hand pressure, improving shot-to-shot consistency during rapid strings and reducing point-of-aim shift under sustained fire. M-LOK integration enables rapid mounting of lights, lasers, foregrips, and other tactical accessories without rail removal or tool changes. The midnight bronze finish provides a non-reflective appearance and corrosion resistance superior to bare steel in field conditions.

This configuration suits operators building a rifle around a specific bolt carrier, trigger, or charging handle preference, as well as those upgrading existing uppers to a quality CMMG platform. LEOs running standardized rifle platforms benefit from the ability to integrate department-approved components. Competitive shooters and serious trainers favor the 5.56 NATO standard and modularity for adapting to various shooting disciplines. The compact barrel length makes this platform relevant for home defense scenarios where overall weapon length remains tactically important.