G
griffen679_180would buy again
Reviewed on May 6, 2026
great machining
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Cmmg Ar-15 Mk4 Receiver Extension Kit
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CMMG
Overview
The CMMG AR-15 Mk4 Receiver Extension Kit is a comprehensive parts kit designed for building a carbine-style AR-15. This kit includes a Mil-Spec buffer tube that ensures compatibility with various components, providing reliable function and performance in your build. It is commonly found in carbine gas system builds chambered in 5.56 NATO, making it a solid choice for standard AR-15 configurations.
Specifications
MPN55CA9D7
AssemblyParts Kit
ColorBlack
Buffer Tube SpecMil-Spec
Buffer Tube TypeCarbine
Frequently Built With
Based on build data
Build Configuration Breakdown
Aggregated and anonymized data showing how builders use this product
PlatformBased on real build data showing which platform (AR-15, AR-10, AR-9) builders pair with this product.
100%
AR-15100%
| Product | Category | Times Built Together |
|---|---|---|
| CMMG AR-15 HD Pivot and Takedown Pin Parts Kit - 55AFF3B | 18 | |
| CMMG AR-15 Carbine Buffer Assembly - 55CA977 | 14 | |
| Strike Industries Flat Wire Spring for AR Carbine - AR-FWS-C | 10 | |
| CMMG AR15 Ambi Mag Catch, Black - 55AFF6E | 9 | |
| Fortis Lightweight Enhanced AR-15 End Plate, Gold - LE-BLK-K1-GOLD | 9 | |
| Magpul Moe K2 Grip Polymer Gray | 8 |
| Platform | Percentage |
|---|---|
| AR-15 | 100% |
Builds Featuring This Part
See all 5 →Builds in the community that include the Cmmg Ar-15 Mk4 Receiver Extension Kit
| Build | Parts | Total |
|---|---|---|
 | 29 | $1695.64 |
 | 19 | $657.06 |
 | 24 | $938.44 |
 | 24 | $1192.01 |
 | 17 | $1685.27 |
Customer reviews
5.0out of 5
1 global rating