CMMG 30BC40AMB Resolute MK4 300 Blackout 16.10", Midnight Bronze, M-LOK Free-Float Handguard for AR-Platform (No BCG or Charging Handle)

The CMMG 30BC40AMB Resolute MK4 300 Blackout 16.10" upper receiver is purpose-built for shooters who demand subsonic rifle capability without the length penalty of a full-size platform. This mid-length upper addresses a critical gap in the modern tactical rifle market: delivering the ballistic advantages of .300 Blackout in a compact, maneuverable package ideal for close-quarters operations, home defense, and specialized law enforcement applications. The 16.10" barrel length positions this upper at the threshold of supersonic and subsonic performance, offering flexibility for both loaded ammunition types while maintaining a profile that doesn't compromise handling in confined spaces.

Built on CMMG's proven Resolute platform, this upper features a free-floating M-LOK handguard that decouples barrel harmonics from rail contact, reducing point-of-impact shifts during sustained fire and improving accuracy consistency—critical in scenarios where reliability determines outcomes. The Midnight Bronze Cerakote finish provides both aesthetic appeal and enhanced corrosion resistance, standing up to moisture, salt spray, and the chemical environments of tactical training. At 3.92 lbs for the upper assembly, the balance and ergonomic profile favor rapid target acquisition and reduced shooter fatigue during extended operations. The free-float design, combined with M-LOK compatibility, allows for modular accessory mounting without impacting barrel performance.

This upper integrates seamlessly with any standard AR-15 lower receiver, making it an ideal upgrade or build component for operators already invested in the platform. Law enforcement tactical teams, military personnel, and civilian marksmen will appreciate the .300 Blackout's subsonic suppressor-ready ballistics and proven terminal performance. Note that this upper does not include a bolt carrier group or charging handle, allowing you to specify components matching your exact performance and reliability requirements. Installation requires only standard AR-15 assembly knowledge, and the modular design ensures compatibility with existing optics mounts, grips, and stock systems.