The Brownells BRN-4/M27 5.56×45 16.5-inch Chrome-Lined AR-15 Barrel (Brownells part no. BN-BRN4556-16H-BL-CL) recreates the classic M16A2-pattern barrel profile for shooters building a retro or duty-style AR-15 upper. Brownells chrome-lines the bore for corrosion resistance and easier cleaning, then phosphates the exterior for a durable, low-maintenance finish that matches period-correct retro builds. The medium-weight profile keeps the barrel from being front-heavy while still giving the chrome lining room to handle sustained strings of fire. A 1-in-7 twist stabilizes today’s heavier 5.56 and .223 loads, including longer tracer and match bullets, better than the slower twist rates found on older service rifles.

Key Specifications

• The barrel is chambered in 5.56x45mm and also safely fires .223 Remington.
• It measures 16.5 inches long in a medium-weight profile.
• Rifling twist is 1-in-7, stabilizing heavier 5.56 bullet weights.
• The bore is chrome-lined for corrosion resistance and easier cleaning.
• The exterior wears a phosphate finish for durability that matches retro M27/M16A2-pattern builds.

Frequently Asked Questions

What twist rate does this barrel use? It uses a 1-in-7 twist, which stabilizes the full range of common 5.56/.223 bullet weights including heavier match and tracer loads.

Is the bore chrome-lined? Yes, the bore is chrome-lined for corrosion resistance and simpler cleaning, a common upgrade over a bare phosphate or nitride bore.

Buy the Brownells BRN-4/M27 16.5-inch AR15 Barrel

Brownells built the BRN-4/M27 profile for shooters who want a period-correct, chrome-lined barrel on a retro or duty AR-15 build. Browse our full AR15 barrels selection and order yours from our Lubbock, Texas gun shop for fast, insured shipping.