Brn-4 Piston Upper Receiver Kits - Brn-4 10.4" Upper Receiver KIT W/ Medium Profile Barrel

Name: Brownells Brn-4 Piston Upper Receiver Kits - Brn-4 10.4" Upper Receiver KIT W/ Medium Profile Barrel
Brand: Brownells
SKU: brownells-brn-4-piston-upper-receiver-kits-brn-4-10-4-upper-receiver-kit-w-medium-profile-barrel-d726f2
Price: 1839.99 USD
Availability: OutOfStock

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Overview

The Brn-4 Piston Upper Receiver Kit from Brownells is a complete assembly designed for the AR-15 platform, featuring a 10.4-inch medium profile barrel. This upper receiver kit allows builders to take advantage of a piston-driven system, which can enhance reliability and reduce the amount of fouling in the action. It's commonly used in builds focused on compactness and maneuverability, making it suitable for both tactical applications and close-quarters engagements.

Specifications

PlatformAR-15

Barrel Length10.4

AssemblyComplete

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Brn-4 Piston Upper Receiver Kits - Brn-4 10.4" Upper Receiver KIT W/ Medium Profile Barrel

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Prices checked Oct 12, 2026

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Build history on GunPartPicker

Builders have been adding the Brownells Brn-4 Piston Upper Receiver Kits - Brn-4 10.4" Upper Receiver KIT W/ Medium Profile Barrel to their builds on GunPartPicker since February 2026. All time, it ranks #398 of the 1,714 upper receivers builders have added.

Today the one retailer we track is out of stock. Listed prices start at $1,839.99 at Brownells for when it comes back.

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Updated Oct 12, 2026 · from real builds on GunPartPicker · Prices checked Oct 12, 2026 · refreshed daily across 37 retailers