CMMG RESOLUTE MK4 Upper — 300 Blackout, 16.10" Barrel, Midnight Bronze, M-LOK Free-Float Handguard (No BCG/Charging Handle) — 30BC40AMB

Build the .300 BLK carbine you’ve always wanted with the CMMG RESOLUTE MK4 upper. Chambered in 300 Blackout and sporting a versatile 16.10" barrel, this factory-assembled upper pairs CMMG reliability with a premium Midnight Bronze finish and a lightweight M-LOK® free-float handguard. It ships without a bolt carrier group (BCG) or charging handle, giving you complete control over the internals and feel of your build. From suppressed training to home/ranch defense and range days with supers or subs, this MK4 upper is a rock-solid foundation for any AR-15 project.

Why This Upper Rocks for 300 BLK

• CMMG precision: Known for clean machining, smart gas tuning, and dependable cycling.

• 300 Blackout versatility: Run supersonic for expanded range/energy or subsonic for quieter, softer recoil—especially when suppressed (where legal).

• 16.10" barrel balance: Practical length for velocity and low blast, with fast handling and easy accessory mounting.

• Free-float M-LOK handguard: Protects barrel harmonics for improved accuracy; mount lights, QD cups, and grips exactly where you need them.

• Midnight Bronze finish: Tough, low-glare coating with a premium look that resists wear and weather.

• Mod-it-your-way: Ships sans BCG/CH, so you can choose coatings (phosphate, nitride, DLC) and ambi handles to match your preferences.

Key Features at a Glance

• Caliber: 300 AAC Blackout (7.62x35mm)

• Barrel Length: 16.10"

• Handguard: M-LOK free-float, slim profile for heat management and accessory placement

• Finish: Midnight Bronze upper/handguard

• Included: Upper receiver group with barrel, gas system, handguard, and muzzle device (configuration may vary by lot)

• Not Included: BCG and charging handle

• Platform: AR-15 / MK4 (Mil-Spec pattern)

• SKU / Model: 30BC40AMB

• UPC: 810103473430

Spec Notes: Common industry specs for this category include 1/2"-28 or 5/8"-24 muzzle threads (300 BLK is typically 5/8"-24), a .750" gas block journal, and a fast twist rate to stabilize heavy subsonics. Confirm your unit’s exact twist, gas system length, and thread pitch against your build plan.

Performance You Can Feel

The free-float handguard eliminates pressure on the barrel for repeatable accuracy, while CMMG’s gas system tuning—paired with your chosen BCG and buffer—supports reliable function across supersonic and subsonic loads. The result is an upper that points quickly, tracks flat, and holds zero, whether you’re running an unsuppressed range session or a suppressed night class (where permitted).

Build It Your Way

• Pick your BCG: Phosphate for duty-grade durability, nitride for low-maintenance cleaning, or DLC/NP3 for slick cycling.

• Choose a charging handle: Standard, extended latch, or ambidextrous for better manipulations around lights/optics.

• Tune the muzzle: Add a flash hider, compensator, brake, or suppressor mount on the correct thread (verify).

• Accessorize smart: Top Picatinny for optics; M-LOK slots for light, pressure pad, QD sling sockets, and a compact hand stop.

Ideal Use Cases

• Home/Ranch Defense: Low-flash, low-blast 300 BLK loads shine in shorter dwell setups.

• Suppressed Shooting: Subsonic compatibility (where legal) with proper gas/buffer tuning.

• Training & Range: Free-float accuracy and modular rails for mission-driven accessories.

• Custom Projects: Premium upper for your favorite lower, trigger, and stock.

Installation Tips

1. Headspace check: When installing your selected bolt, verify headspace before live fire.

2. Muzzle device timing: Use a new crush washer or shims and torque to spec.

3. Gas/buffer tuning: Match buffer/spring and gas for your chosen super/sub loads and suppressor use.

4. Fastener discipline: Torque rail and accessory screws per spec and use threadlocker where recommended.

Care & Maintenance

• Break-in: Modern barrels generally need minimal break-in—prioritize quality lubrication and consistent ammo.

• Cleaning: Keep chamber, extension lugs, and gas system clean; periodically inspect handguard screws.

• Finish care: Wipe Midnight Bronze surfaces with a light oil after wet or salty conditions.

Specifications (Summary)

• Brand: CMMG

• Series: RESOLUTE MK4

• Caliber: 300 AAC Blackout

• Barrel: 16.10"

• Handguard: M-LOK free-float

• Finish: Midnight Bronze

• Includes: Upper assembly (barrel, gas system, handguard, muzzle device)

• Excludes: BCG & charging handle

• Model/SKU: 30BC40AMB

• UPC: 810103473430

SEO-Optimized Highlights

• CMMG RESOLUTE MK4 300 Blackout upper, 16.10" barrel

• Midnight Bronze finish with M-LOK free-float handguard

• Ships without BCG or charging handle for custom builds

• 30BC40AMB, UPC 810103473430

• Premium AR-platform upper for subs/supers, defense, and training

Suggested Meta Title

CMMG RESOLUTE MK4 300 Blackout Upper — 16.10", Midnight Bronze, M-LOK (No BCG/CH) | 30BC40AMB

Suggested Meta Description

Build smarter with the CMMG RESOLUTE MK4 300 Blackout upper. 16.10" barrel, Midnight Bronze finish, M-LOK free-float handguard; ships without BCG/charging handle for custom configurations. SKU 30BC40AMB, UPC 810103473430.

Suggested Image Alt Text

“CMMG RESOLUTE MK4 300 Blackout upper, 16.10-inch barrel, Midnight Bronze with M-LOK free-float handguard (30BC40AMB)”

Safety & Compliance: Assemble on an unloaded firearm. Verify torque, headspace, and function before defensive use. Follow all federal, state, and local laws—especially those regarding suppressors and ammunition.

Midnight Bronze durability, free-float accuracy, and true 300 BLK versatility—CMMG’s RESOLUTE MK4 upper is the perfect core for your next AR build. The End