Brownells Brn-16A4 5.56X45 Nato 20'' Bbl Upper Receiver

The Brownells BRN-16A4 upper receiver is a faithful reproduction of the classic M16A4 platform, built for shooters who want authentic mil-spec performance with modern manufacturing reliability. This 20-inch 5.56x45mm NATO upper is designed as a complete, ready-to-pair component—drop it onto your lower receiver and you're halfway to a functional rifle that honors the original A4 design without cutting corners on parts quality.

What makes the BRN-16A4 stand out is its commitment to the original specification. The upper receiver itself lacks M4 feed ramps, just like genuine A4 uppers, ensuring compatibility with traditional A2-pattern lowers. The 20-inch Government-profile barrel features a 1-7 twist rate and chrome-lined bore and chamber, optimized to shoot M855 62-grain rounds and heavier projectiles reliably. The muzzle is capped with an M16A2 flash hider that performs as well as it looks. A proper "F" marked front sight base carries the correct A2 square post, bayonet lug, and sling swivel—practical features that collectors and purists appreciate.

The included bolt carrier group comes phosphate-finished on the exterior with a chrome-lined bore and gas key interior, delivering the durability expected in a mil-spec build. Handguards ship with a heat shield and replicate the ergonomics and appearance of original A2 units. Because the upper uses a standard USGI barrel nut, you're not locked into Brownells-specific accessories down the road; plenty of aftermarket handguards, rail systems, and upgrades will fit if you ever want to modernize. This is a new-production upper receiver, not surplus, so you're starting with components manufactured to consistent standards.

The BRN-16A4 appeals to M16A4 builders, military history enthusiasts, and shooters who want a 20-inch rifle platform without paying surplus prices or chasing rare original military parts. Pair it with a compatible lower receiver, add furniture and a charging handle, and you have a classic American rifle that still runs.

Key Features

• M16A4 specification upper receiver without M4 feed ramps
• 20-inch Government-profile 5.56x45mm NATO barrel with 1-7 twist
• Chrome-lined bore and chamber for corrosion resistance and longevity
• M16A2 flash hider reduces muzzle flash
• F-marked front sight base with A2 square post, bayonet lug, and sling swivel
• Mil-spec phosphate bolt carrier group with chrome-lined gas key
• Standard USGI barrel nut accepts most aftermarket handguards and rail systems
• Included M16A2-style handguards with heat shield
• New production (no surplus parts)

Specifications

Frequently Asked Questions

What lower receiver is compatible with the BRN-16A4 upper?

The BRN-16A4 is designed to pair with any standard A2-pattern lower receiver. Because the upper does not feature M4 feed ramps, it works best with traditional A2 or A4 lowers; compatibility with modern M4 lowers depends on their specific feed ramp design. Always verify fitment with your chosen lower before assembly.

Can I upgrade the handguards and rail system later?

Yes. The BRN-16A4 uses a standard USGI barrel nut, so a wide variety of aftermarket handguards, rail systems, and accessories are compatible. You can start with the included M16A2 handguards and swap them out whenever you want without replacing the barrel nut.

What ammunition does this barrel shoot best?

The 1-7 twist rate is optimized for M855 62-grain rounds and heavier bullets. It will cycle lighter rounds, but heavier projectiles stabilize better through this twist rate.

Is the bolt carrier group included?

Yes. The BRN-16A4 ships with a mil-spec phosphate bolt carrier group featuring a chrome-lined bore and gas key interior.