CMMG M16 / AR-15 5.56 NATO Complete Bolt Carrier Group - Black Nitride - 55BA419 - UPC 852005002431
Product Description
The CMMG M16 5.56 NATO Complete Bolt Carrier Group (55BA419) is a premium, full-auto profile cycling assembly engineered for absolute mechanical reliability in AR-15, M4, and M16 platform rifles. Built to withstand continuous high-volume fire and severe operational stress, this complete assembly includes the bolt carrier, full bolt assembly, gas key, cam pin, firing pin, and retaining pin—delivering a turnkey drop-in replacement or core component for custom rifle builds.
The full-auto profile bolt carrier is precision-machined from high-strength steel and features an advanced salt bath Black Nitride finish (QPQ). This slick, ultra-hard surface treatment penetrates the metal surface, dramatically increasing wear resistance, reducing mechanical friction, and easing carbon buildup cleanup compared to traditional phosphate coatings. The bolt itself is crafted from high-grade Carpenter 158 steel, shot-peened for enhanced fatigue life, and high-pressure tested (HPT) and magnetic particle inspected (MPI) to guarantee zero microscopic material defects.
Engineering details include a properly staked, heat-treated gas key secured with grade-8 fasteners to prevent gas leakage or backing out under rapid firing schedules. Complete with a heavy-duty extractor spring, crane o-ring, and durable extractor, the CMMG 55BA419 BCG ensures crisp, positive extraction and smooth cycling across 5.56 NATO, .223 Remington, and .300 AAC Blackout chamberings.
*Armorer Bench Notes & Real-World Staging Guidance:
Fitment Matrix: Direct fit for all standard Mil-Spec AR-15, M4, and M16 upper receivers chambered in 5.56 NATO, .223 Remington, .300 AAC Blackout, or .204 Ruger. Note: Full-auto profile adds mass to delay unlock timing and smooth out cycling impulses in both semi-automatic and full-automatic receiver configurations. Fully legal for civilian ownership in semi-auto rifles.
- Verify upper receiver bore and barrel extension are clean, dry, and free of obstruction before inserting the BCG.
- Apply a light coat of synthetic firearm oil or grease to carrier slide rails, cam pin slot, and bolt body friction surfaces.
- Insert BCG into upper receiver with bolt face extended forward; verify smooth gas tube engagement with the gas key during forward travel.
Key Features
- Full-Auto M16 Carrier Profile: Increased carrier mass delays bolt unlock time, reducing felt recoil and smoothing out operational cycling.
- Salt Bath Black Nitride Finish (QPQ): Ultra-hard, corrosion-resistant surface treatment provides extreme slickness and effortless carbon cleanup.
- Carpenter 158 Steel Bolt Assembly: High-strength, heat-treated bolt shot-peened for long-term structural fatigue resistance.
- HPT & MPI Inspected: High-Pressure Tested and Magnetic Particle Inspected to ensure flawless metallurgical integrity.
- Properly Staked Gas Key: Heat-treated gas key secured with grade-8 fasteners and dual-point staking to prevent gas leakage.
- Multi-Caliber Compatibility: Cycles reliably across 5.56 NATO, .223 Remington, and .300 AAC Blackout platforms.
Product Specifications
- Brand: CMMG
- Model: M16 5.56 NATO Complete Bolt Carrier Group
- MPN / Part Number: 55BA419
- UPC: 852005002431
- Caliber Compatibility: 5.56x45mm NATO / .223 Remington / .300 AAC Blackout
- Carrier Profile: M16 Full-Auto Profile
- Bolt Material: Carpenter 158 Steel
- Carrier Material: 8620 Alloy Steel
- Testing: High Pressure Tested (HPT) / Magnetic Particle Inspected (MPI)
- Finish / Color: Black Nitride (QPQ)
- Mass: ~11.6 oz (328.8 g)
