R
RhettRider370CMMG BCG glossy finish
Reviewed on May 3, 2026
CMMG 5.56 BCG runs reliably on a carbine 16in build. The black finish is more glossy than the matte I expected from product photos, only visible side by side. Gas key staked properly.
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CMMG
Overview
The CMMG 5.56 Complete Bolt Carrier Group is designed for the 5.56 NATO caliber, ensuring reliable cycling and performance in your AR-15 build. With a nitride finish, this BCG enhances durability and corrosion resistance, contributing to smoother operation and easier maintenance. This component is often found in mid-length gas system builds, making it a solid choice for those looking to optimize their rifle's performance.
Specifications
MPN55BA419
Caliber5.56 NATO
FinishNitride
CMMG 5.56 Complete Bolt Carrier Group, Black - 55BA419
Available Merchants(7)
Prices checked
Price Alert
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October 2026 on GunPartPicker
CMMG 5.56 Complete Bolt Carrier Group, Black - 55BA419 ranked #36 of the 258 bolt carrier groups builders added on GunPartPicker in October 2026. Builders have added it to their builds on GunPartPicker. Since April 2026, it ranks #50 of the 552 bolt carrier groups builders have added. Builds with this bolt carrier group are mostly chambered in 5.56 NATO (81%, then .223 Wylde 8%), split between carbine-length (42%) and mid-length (35%) gas systems, and nearly all AR-15.
Availability is good: it was in stock at one retailer or another nearly every time we checked in October 2026, and today 4 of the 7 retailers we track have it in stock. It dipped to $128.36 at Classic Firearms for a stretch in October 2026, under its usual $133.99 to $139.49, so sales do come around. Buying today, the lowest price is $139.99 at Optics Planet, above October's low of $128.36, so a better deal may come back.
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Frequently Built With
The part most often added in each category by the builds that include this one
Tacfire AR-15 Stripped Upper Receiver - Minus BCG
Upper Receiver$70in 6% of them
Wilson Combat AR-15 Lower Receiver Forged
Lower Receiver$100 · out of stockin 6% of them
CMMG AR15 Charging Handle Assembly, Black - 55BA5EC
Charging Handle$28in 9% of them
CMMG AR-15 Mil-Spec Trigger KIT
Trigger$31in 12% of them
Magpul MOE SL-M Carbine Stock Mil-Spec FDE
Stock & Brace$35in 6% of them
Rosco Bloodline AR-15 16" 556 Barrel, 1:7 Twist - BL16M45567C
Barrel$167in 6% of them
Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
CaliberBased on real build data showing which calibers builders choose alongside this product.
80.6%
5.56 NATO80.6%
.223 Wylde8.3%
6mm ARC5.6%
.223 Remington2.8%
300 Blackout2.8%
Gas SystemBased on real build data showing which gas system lengths builders use with this product.
42.3%
Carbine42.3%
Mid-Length34.6%
Rifle19.2%
Pistol3.8%
Builds Featuring This Part
See all builds →Builds in the community that include the CMMG 5.56 Complete Bolt Carrier Group, Black - 55BA419
| Build | Parts | Total |
|---|---|---|
 | 15 | $3511.57 |
 | 17 | $1472.22 |
 | 14 | $859.09 |
 | 13 | $2982.88 |
 | 21 | $979.14 |
 | 25 | $1064.91 |
Customer reviews
4.0out of 5
1 global rating
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