Brownells Brn-4 5.56X45 10.4'' Medium Chrome Lined Barrel, Phosphate

The Brownells BRN-4 5.56x45 10.4" medium profile barrel is a chrome-lined, phosphate-finished component engineered for builders working with HK 416-compatible platforms. Machined by Faxon, this barrel delivers the reliability of a proven design in a lighter, more maneuverable package than its heavy counterpart. The 10.4" length makes it well-suited for short-stroke piston systems, CQB-oriented builds, or compact tactical rifles where weight savings and handling matter without sacrificing barrel rigidity.

Built with button rifling and a 1-7 twist rate, this barrel reliably cycles both 5.56x45mm NATO and .223 Remington ammunition—giving you flexibility at the range or in the field. The ½-28 muzzle threads accept standard suppressors, muzzle brakes, and flash hiders, so you can configure the muzzle end to suit your mission. The phosphate finish provides a hard, corrosion-resistant exterior and interior surface that's straightforward to clean and maintain through heavy use.

Installation is straightforward with the BRN-4 barrel nut (torque spec: 50–80 ft/lbs), and the extended barrel extension ensures a solid interface with early-generation HK 416 upper receivers. All BRN-4 barrels share the same piston rod assembly, simplifying your parts selection—just match the correct gas block to your barrel length for hassle-free integration. Whether you're a long-time HK platform enthusiast or a first-time builder, this barrel removes the historical scarcity that once made HK 416-compatible components nearly impossible to source.

Key Features

• Faxon-machined, chrome-lined barrel for durability and ease of cleaning
• Medium profile reduces weight while maintaining rigidity
• 10.4" length ideal for short-stroke piston platforms and compact builds
• Button-rifled with 1-7 twist for reliable cycling of 5.56x45mm NATO and .223 Remington
• ½-28 muzzle threads for suppressors, brakes, and flash hiders
• Phosphate finish resists corrosion and wear
• HK 416 upper receiver compatible (early generations)
• Works with standard BRN-4 piston rod assembly and matched gas blocks

Specifications

Frequently Asked Questions

Will this barrel work with my HK 416 upper?

Yes, this barrel is designed for early-generation HK 416 upper receivers. The extended barrel extension ensures a robust fit with those receivers. Use the BRN-4 barrel nut for installation.

What gas block do I need for a 10.4" barrel?

All BRN-4 barrels use the same piston rod assembly, so compatibility depends on matching the correct gas block to your barrel length. Consult Brownells' BRN-4 component lineup (search "BRN-4") to select the gas block rated for 10.4" barrels.

Can I shoot both 5.56 NATO and .223 Remington through this barrel?

Yes. This barrel is chambered in 5.56x45mm NATO and will reliably cycle both NATO-spec 5.56x45mm and .223 Remington ammunition.

What muzzle devices fit the ½-28 threads?

The ½-28 muzzle thread is a common standard that accepts most commercial suppressors, muzzle brakes, flash hiders, and other muzzle attachments with ½-28 specs. Verify your device matches this thread pitch before installation.