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

Discover the precision and reliability of the Green Mountain 5.56 AR-15 Barrel 20″ M16 A1 Phosphate. Engineered for serious shooters and builders, this barrel delivers consistent performance in a classic M16 A1 configuration, making it an ideal choice for retro builds, tactical applications, or range-ready AR-15 platforms.

Key Features

• Chrome-lined bore and chamber with phosphate exterior finish for exceptional durability and corrosion resistance, ensuring long service life even under heavy use.
• Government / SOCOM profile provides a balanced blend of strength and manageable weight for stable handling and accuracy.
• 1:7 twist rate stabilizes a wide range of 5.56 NATO and .223 Remington projectiles, including heavier match loads for improved downrange performance.
• Rifle-length gas system with 0.625″ gas block journal promotes smooth cycling and reduced recoil for reliable operation.
• 1/2×28 muzzle threading allows easy attachment of suppressors, flash hiders, or other muzzle devices.

Technical Specifications

• Barrel Length: 20 inches
• Cartridge Compatibility: 5.56 NATO
• Platform: AR-15
• Finish: Phosphate + Chrome Lined
• Gas System: Rifle
• Twist Rate: 1:7
• Muzzle Thread: 1/2×28
• Weight: 35.4 oz

Benefits for Your Build

This barrel addresses common pain points like barrel wear, inconsistent accuracy, and compatibility issues by combining mil-spec construction with modern features. The chrome lining protects against the heat and pressure of sustained fire, while the phosphate finish offers a non-reflective, rugged exterior suited for tactical environments. Whether you’re restoring an M16 A1 clone or upgrading an existing AR-15, the rifle-length gas system ensures dependable function across various ammunition types.

Constructed from high-quality 41V50 steel, it maintains tight tolerances for superior shot-to-shot consistency without unnecessary bulk.

Why Choose This Barrel?

Green Mountain barrels are trusted by builders for their attention to detail and proven track record in accuracy and longevity. This 20″ model offers the reach and ballistic advantages of a full-length barrel while maintaining compatibility with standard AR-15 components.

Upgrade your rifle with this premium barrel today and experience the difference in build quality and performance.