Green Mountain 5.56 AR-15 Barrel 11.5" M4 A1 Phosphate - GM-M64

Upgrade your AR-15 build with the Green Mountain 5.56 AR-15 Barrel 11.5″ M4 A1 Phosphate. This precision-engineered barrel delivers reliable performance in a compact package ideal for SBRs, pistols, and tactical configurations. Crafted from high-quality 4150 chrome moly vanadium steel, it features a durable phosphate finish over a chrome-lined bore and chamber for exceptional corrosion resistance and extended service life under demanding conditions.

Key Features and Benefits

• M4 Profile Design: Provides an optimal balance of strength and reduced weight, enhancing maneuverability without sacrificing durability for close-quarters or dynamic shooting scenarios.
• Chrome-Lined Bore and Chamber: Ensures superior resistance to wear, fouling, and corrosion while maintaining accuracy over thousands of rounds, making it a dependable choice for high-volume training or duty use.
• 1:7 Twist Rate: Stabilizes a wide range of bullet weights from 55 to 77 grains, delivering consistent accuracy and reliable terminal performance across various ammunition types.
• Carbine-Length Gas System: Promotes smooth, reliable cycling in shorter barrel lengths, minimizing recoil and supporting consistent function with standard AR-15 components.
• Phosphate Finish: Offers a rugged, non-reflective coating that protects against environmental elements while maintaining a professional tactical appearance.

Technical Specifications

• Barrel Length: 11.5 inches
• Caliber: 5.56 NATO / .223 Remington
• Twist Rate: 1:7
• Gas System: Carbine length
• Gas Block Journal: 0.750 inches
• Muzzle Thread: 1/2×28
• Profile: M4 contour
• Finish: Phosphate with chrome-lined bore and chamber
• Material: 4150 CMV steel
• Weight: 24.8 ounces

Why Choose the Green Mountain 11.5″ M4 Barrel?

This barrel addresses common challenges in compact AR builds by combining proven military-inspired geometry with modern manufacturing standards. The M4 A1 profile and carbine gas system ensure reliable operation even with suppressors or varying ammunition, while the chrome lining extends barrel life far beyond standard options. Whether you’re assembling a home-defense pistol or a lightweight carbine, this component provides the foundation for a high-performing firearm.

Engineered for enthusiasts and professionals alike, the Green Mountain barrel integrates seamlessly with standard AR-15 uppers, offering precision rifling and consistent headspacing for safe, accurate shooting.

Ideal Applications

Perfect for builders seeking a compact, reliable 5.56 barrel that excels in both accuracy and durability. Its specifications make it suitable for a variety of platforms, from personal defense weapons to competition setups requiring quick handling.