Brownells Ar-15/M16A1 Retro Carbine 5.56Mm 11.5'' 1-7 Bbl Assembly

The Brownells AR-15/M16A1 Retro Carbine 5.56mm 11.5" 1-7 barrel assembly brings authentic 1960s–2000s carbine proportions to modern builds. Whether you're recreating a period-correct XM177 or need a lightweight, quick-handling barrel for a compact AR platform, this retro-profiled assembly delivers both historical accuracy and practical performance. Machined from ordnance-grade 4150 chrome-moly steel with a hard black phosphate finish, it's built to last and designed to feel like the original article.

The 11.5" barrel is chambered in 5.56 NATO with a 1-7" twist rate, meaning it cycles modern ammunition reliably and stabilizes everything from lighter varmint rounds to heavier tactical loads. The chrome-lined bore resists fouling and extends barrel life—a detail that matters on a retro build where you want the gun to actually shoot, not just look the part. At this length, you get meaningful velocity retention over a pistol barrel while keeping overall package size down for handy, nimble handling.

Everything you need comes pre-installed: carbine-length gas tube, front-sight base (.625" diameter, marked F), sight post, detent, spring, sling swivel, bayonet lug, Delta ring, barrel nut, weld spring, snap ring, and round handguard cap. The muzzle is threaded 1/2"-28 TPI, ready for a retro flash hider or any modern suppressor or brake. Pair this with a carbine-length upper receiver and you're on your way. Remember: if you plan to shoot this as a short-barreled rifle (SBR), you're responsible for all NFA compliance and registration.

Brownells barrels are magnetic particle inspected at the factory to catch hidden flaws before they leave the shop—a level of QC that keeps your build reliable from day one.

Key Features

• 11.5" carbine-length barrel with authentic A1 profile
• 5.56 NATO chamber with 1-7" twist rifling
• Chrome-lined bore for durability and easy cleaning
• 4150 chrome-moly steel with hard black phosphate finish
• Carbine-length gas system with .070" gas port
• Pre-installed front-sight base with bayonet lug, sight post, detent, and spring
• 1/2"-28 TPI muzzle threads for modern or period-correct devices
• Includes barrel nut, Delta ring, sling swivel, and handguard cap
• Magnetic particle inspected for hidden flaws

Specifications

Frequently Asked Questions

Is this barrel assembly legal as an SBR?

At 11.5", this barrel falls into short-barreled rifle territory and is subject to NFA regulations. You are responsible for ensuring full compliance with all federal, state, and local laws before assembly or use.

Can I use this with 223 Remington ammunition?

The barrel is chambered in 5.56 NATO. While 5.56 NATO chambers typically accept .223 Remington, you should always verify compatibility with your specific firearm and ammunition.

What gas tube length do I need?

This assembly uses a carbine-length gas system, so you'll need a carbine-length gas tube to complete your build.

What muzzle devices can I attach?

The barrel is threaded 1/2"-28 TPI, which accepts both period-correct A1-style flash hiders and modern suppressors, brakes, and compensators in that thread pitch.

Is a bayonet lug included?

Yes, this assembly includes a bayonet lug on the front-sight base.