Geissele AR15/M4 Reaction Block (Mil-Spec Buffer Tube Only) 05-314

Geissele AR15/M4 Reaction Block (Mil-Spec Buffer Tube Only)  05-314 - Buffer Tube Assembly for AR-15 - view 1
Geissele AR15/M4 Reaction Block (Mil-Spec Buffer Tube Only)  05-314 - Buffer Tube Assembly for AR-15 - view 2
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Geissele

Overview

The Geissele AR15/M4 Reaction Block is a Mil-Spec buffer tube designed as a tube only assembly, providing a reliable foundation for your AR-15 build. This buffer tube is critical for proper function and cycling of the action, ensuring compatibility with Mil-Spec components and accessories. Commonly seen in builds featuring a mid-length gas system and chambered in 5.56 NATO, this component is essential for achieving a smooth and reliable shooting experience.

Specifications

MPN05-314
AssemblyTube Only
Buffer Tube SpecMil-Spec

Available Merchants(6)

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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

93.8%
AR-1593.8%
AR-96.3%

Caliber

76.5%
5.56 NATO76.5%
.223 Wylde11.8%
.450 Bushmaster11.8%

Gas System

57.9%
Mid-Length57.9%
Carbine21.1%
Rifle15.8%
Pistol5.3%
Frequently Built With Products
ProductCategoryTimes Built Together
Bravo Company Manufacturing Mk2 Recoil Mitigation System - Mod 1 - T212
Sprinco Usa Reduced Power Kit Buffer 4-Coil Bolt Extractor Spring9
Fortis Lightweight Enhanced AR-15 End Plate, Gold - LE-BLK-K1-GOLD9
Radian Forward Assist - 7075 Aluminum - BlackForward Assist8
Jp Enterprises Silent Captured Spring for Law Tactical Folder8
Geissele Automatics Llc Ar-15 Ultra Precision 5 Axis Trigger Guard Ddc8
Build Platform Breakdown
PlatformPercentage
AR-1593.8%
AR-96.3%
Build Caliber Breakdown
CaliberPercentage
5.56 NATO76.5%
.223 Wylde11.8%
.450 Bushmaster11.8%
Build Gas System Breakdown
Gas SystemPercentage
Mid-Length57.9%
Carbine21.1%
Rifle15.8%
Pistol5.3%

Builds Featuring This Part

See all 5

Builds in the community that include the Geissele AR15/M4 Reaction Block (Mil-Spec Buffer Tube Only) 05-314

BuildPartsTotal
20" noveske clone
25$2495.43
Second 5.56 build
28$5330.29
8" SBR
24$3653.74
SBR 16.5" 5.56
32$2612.49
Franklin armory 11.5" 5.56
36$16188.80

Customer reviews

4.0out of 5

2 global ratings

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Top reviews

T
tehWildGinger
small things to mention
Reviewed on April 28, 2026Verified with Build

good stock but the adjustment lever was stiff for the first week of use

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I
i_likebuilding91
Geissele reaction block heavy
Reviewed on March 26, 2026Verified with Build

Geissele AR15 reaction block fits a milspec buffer tube. Used for clamping uppers in a vise without marring. Heavier than I expected from a small accessory but the solid steel construction is reassuring. Worth it if you do your own armorer work.

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