CMMG

Cmmg Ar-15 Mk4 Receiver Extension Kit

Cmmg Ar-15 Mk4 Receiver Extension Kit - Buffer Tube for AR-15 - view 1
Cmmg Ar-15 Mk4 Receiver Extension Kit - Buffer Tube for AR-15 - view 2
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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

Available Merchants(9)

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Frequently Built With

Based on build data

Build Configuration Breakdown

Aggregated and anonymized data showing how builders use this product

Platform

100%
AR-15100%
Frequently Built With Products
ProductCategoryTimes Built Together
CMMG AR-15 HD Pivot and Takedown Pin Parts Kit - 55AFF3B24
CMMG AR-15 Carbine Buffer Assembly - 55CA97721
Strike Industries Flat Wire Spring for AR Carbine - AR-FWS-C15
CMMG AR15 Ambi Mag Catch, Black - 55AFF6E12
Fortis Lightweight Enhanced AR-15 End Plate, Gold - LE-BLK-K1-GOLD11
Wilson Combat Ar-15 Lower Receiver Forged9
Build Platform Breakdown
PlatformPercentage
AR-15100%

Builds Featuring This Part

See all 5

Builds in the community that include the Cmmg Ar-15 Mk4 Receiver Extension Kit

BuildPartsTotal
carbine 14.5" 5.56
29$1720.82
As a truck gun 30"
19$653.37
14.5" 5.56
24$933.80
Wilson Combat 16" build
24$1211.07
Griffin armament 18"
17$1575.36

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Top reviews

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xwiz
CMMG MK4 ext kit complete
Reviewed on March 23, 2026Verified with Build

CMMG MK4 receiver extension kit includes the buffer tube, spring, castle nut, and end plate. Adjustment lever locks tight at each position. Six positions. Threads to a standard milspec castle nut. Complete kit at a reasonable price.

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