Green Mountain 5.56 AR-15 Barrel 20" M16 A1 Phosphate - GM-M15

Upgrade your AR-15 build with the Green Mountain 5.56 AR-15 Barrel 20″ M16 A1 Phosphate, a precision-engineered component designed for shooters who demand accuracy, durability, and authentic M16-style performance. Crafted to exacting standards, this barrel delivers reliable function in both recreational and tactical applications while supporting modern 5.56 NATO ammunition.

Key Features and Benefits

• Chrome-lined bore and chamber with phosphate exterior finish – Provides exceptional corrosion resistance and extended service life, reducing maintenance needs and ensuring consistent performance in varied conditions.
• Government / SOCOM profile with rifle-length gas system – Offers a balanced weight distribution for improved handling and reduced recoil, ideal for precision shooting or duty use.
• 1:7 twist rate – Optimized for stabilizing a wide range of bullet weights, including heavier projectiles, enhancing accuracy across different loads.
• 0.625″ gas block journal and 1/2×28 muzzle threads – Ensures compatibility with standard low-profile gas blocks and a variety of muzzle devices for custom configurations.
• M16-style extension and 20-inch length – Delivers classic ergonomics and velocity for effective terminal performance at longer ranges.

Technical Specifications

• Platform: AR-15
• Caliber: 5.56 NATO
• Barrel Length: 20 inches
• Twist Rate: 1:7
• Gas System: Rifle length
• Gas Block Journal: 0.625 inches
• Muzzle Thread: 1/2×28
• Finish: Phosphate with chrome-lined bore and chamber
• Barrel Profile: Government / SOCOM
• Weight: 35.4 ounces

Why Choose This Product

This barrel addresses common pain points for AR-15 builders, such as inconsistent accuracy with varying ammunition and premature wear in harsh environments. The robust construction from premium materials ensures tight tolerances for reliable feeding, extraction, and grouping. Whether restoring a classic M16A1 replica or building a modern tactical rifle, it provides the foundation for dependable operation without compromising on quality or compatibility.

Invest in a barrel that combines proven design with contemporary performance enhancements for years of trusted service.