Brownells Ar-15/A1 5.56Mm 20'' 1-7 Twist Rifle Barrel Assembly

The Brownells AR-15/A1 5.56mm 20" 1-7 twist rifle barrel assembly is a purpose-built retro rifle length setup for builders and shooters who want to run authentic A1-style AR-15 builds or just prefer the original platform. This is a complete barrel assembly—not just a tube—so you get everything needed to install it on a stripped upper receiver: the barrel itself, front sight base, gas tube extension, sight post, detent and spring, sling swivel, rivet, delta ring, barrel nut, weld spring, snap ring, and triangular handguard cap. If you're going classic or restoring a rifle to original specs, the legwork is already done.

The barrel is chrome-lined 4150 steel, chambered in 5.56x45 NATO with a 1-7 twist rate that stabilizes the full range of 5.56 loads and heavier bullets. The 20" length is rifle-length gas system spec, and muzzle threads are 1/2-28 for standard A1-style muzzle brakes or flash hiders. Black phosphate finish resists corrosion and matches the retro aesthetic. The .625" No F Marks sight base is correct for A1 uppers and accepts standard AR-15 front sight posts.

This assembly is ideal for retro builds, clones, or shooters who simply prefer the original AR-15 platform for hunting, range work, or general shooting. Because the barrel comes pre-assembled with the extension, front sight, and hardware, you skip the headaches of sourcing compatible parts individually and get a rifle-length setup that's ready to go.

Key Features

• Complete barrel assembly with all necessary components included
• Chrome-lined 4150 steel barrel for durability and ease of cleaning
• 1-7 twist rate suitable for standard and heavier 5.56 ammunition
• 20" rifle-length barrel with rifle-length gas system
• 1/2-28 muzzle threads for A1-style muzzle devices
• Black phosphate finish for corrosion resistance
• Pre-assembled with front sight base, delta ring, handguard cap, and hardware
• Authentic A1 configuration for retro and clone builds

Specifications

Frequently Asked Questions

Will this barrel assembly work with my AR-15 upper receiver?

Yes, this is a standard rifle-length barrel assembly designed for AR-15 A1 uppers. It installs directly into a compatible upper receiver with the barrel nut and all included hardware.

What ammunition can I shoot through the 1-7 twist barrel?

The 1-7 twist rate is suitable for the full range of 5.56x45 NATO ammunition, including standard 55-grain loads and heavier bullet weights.

Is this a complete barrel or do I need additional parts?

This is a complete barrel assembly. It includes the barrel, front sight base, gas tube extension, delta ring, handguard cap, barrel nut, and all necessary springs, detents, and hardware. You only need a stripped upper receiver to install it.

Can I use modern muzzle devices with the 1/2-28 threads?

The 1/2-28 muzzle threads are the original A1 standard. You can use any muzzle device threaded for 1/2-28, though the retro configuration is most authentic with period-correct A1-style flash hiders or brakes.