Brownells Brn-4 Assembled Upper 14.5'' Heavy Chrome Lined Barrel Black

The Brownells BRN-4 assembled upper receiver with 14.5-inch heavy chrome-lined barrel is a complete, ready-to-shoot upper designed for builders who want quality parts without the assembly hassle. Built from new components on a billet upper receiver, this upper pairs a Faxon medium-profile chrome-moly barrel with a purpose-built bolt carrier group and gas system, so you're just a handguard and muzzle device away from a complete AR-15. The heavy profile keeps rounds on target through sustained fire, and the chrome-lined bore has been the standard for hard-use rifles for good reason—durability and easy maintenance in field conditions.

Every component here is engineered for reliability. The barrel, button-rifled from 4150 chrome moly steel with a 1-7 twist, wears a matte black phosphate finish and 1/2-28 muzzle threads for your choice of brake or suppressor. The bolt carrier group uses a one-piece forged 8620 steel carrier, a 9310 tool steel bolt with a hard chrome finish, and a properly installed piston bushing to keep wear minimal. The billet upper receiver is finished in hard coat anodizing, and the barrel is secured with an oversized barrel nut that threads deep into the barrel extension—a design that locks everything down more rigidly than a standard AR-15 upper. Brownells tested-fires every upper before shipping.

Installation is straightforward: slide an HK 416-compatible handguard over the barrel (one bolt to tighten), thread on your 1/2-28 muzzle device, and you're done. Comes with a Magpul ejection port cover and mil-spec charging handle. Brownells recommends pairing it with an H1 or H2 recoil buffer and carbine recoil spring, and using 5.56 NATO ammunition.

Key Features

• Complete assembled upper—barrel, bolt carrier group, and gas system installed
• Faxon 4150 chrome moly barrel, 1-7 twist, chrome-lined bore and chamber
• Heavy profile keeps thermal stability for sustained shooting
• Billet upper receiver machined for precision, hard coat anodized
• One-piece forged 8620 steel carrier; chrome 9310 bolt, headspaced before and after barrel installation
• Oversized barrel nut with extended engagement—more surface area for rigid mounting than standard AR-15
• Piston bushing installed to reduce upper receiver wear
• 1/2-28 muzzle threads; compatible with standard AR-15 muzzle devices
• HK 416-compatible handguard interface
• Magpul ejection port cover and mil-spec charging handle included
• Test-fired before shipment

Specifications

Frequently Asked Questions

What lower receiver does this upper fit?

The BRN-4 upper is designed to fit standard AR-15 lower receivers. You'll need to pair it with an AR-15 lower of your choice to complete your rifle.

What handguard is compatible with the BRN-4?

The upper uses an HK 416-compatible handguard interface. Installation is simple: slide the handguard over the barrel and tighten one bolt. Consult your handguard manufacturer's instructions for best results.

What muzzle devices can I use?

The barrel features 1/2-28 muzzle threads, so any standard AR-15 1/2-28 muzzle device—brake, suppressor, flash hider—will work. Installation is straightforward and compatible with common upper receiver jigs and rods.

What recoil system should I use?

Brownells recommends pairing the BRN-4 upper with an H1 or H2 recoil buffer and carbine recoil spring for optimal operation.

Is this upper already test-fired?

Yes. Every BRN-4 upper is test-fired before shipment. You may notice minor cosmetic signs of firing, such as marks on the shell deflector or slight fouling inside—this is normal and does not affect performance.