The Brownells AR-15 5.56 Mk18 barrel group delivers a professional-grade, ready-to-run upper component built to mil-spec standards. At 10.3 inches, this carbine-length barrel with carbine gas system hits the sweet spot for close-quarters and short-range work—ideal for 3-gun competitors, short-barreled rifle (SBR) builders, and anyone prioritizing maneuverability in confined spaces. The 1-7 twist rifling stabilizes modern 62-grain and heavier ammunition, making it flexible across typical 5.56 NATO loads.

Built by a US Government contractor to exacting standards, this barrel group features a chrome-lined bore applied over button rifling for durability and corrosion resistance. Every barrel undergoes high-pressure testing, magnetic particle inspection, and precision gauging before leaving the factory—no shortcuts, no surprises. The 4150 chrome moly steel construction is proven in military and law enforcement use and holds up to sustained firing and aggressive handling.

The assembly arrives pre-fitted with the slip ring, F-marked front sight base, and handguard cap already installed, so you can integrate it into your upper receiver without extra machining or fitting work. The barrel is chamber-marked 5.56x45mm NATO and carries the mil-spec rib for drop-in compatibility with standard AR-15 uppers. If you're building a compact 5.56 rifle or upgrading an existing platform with a proven, inspected barrel, this Brownells group takes the guesswork out of the process.

The Brownells AR-15 5.56 Mk18 barrel group delivers a professional-grade, ready-to-run upper component built to mil-spec standards. At 10.3 inches, this carbine-length barrel with carbine gas system hits the sweet spot for close-quarters and short-range work—ideal for 3-gun competitors, short-barreled rifle (SBR) builders, and anyone prioritizing maneuverability in confined spaces. The 1-7 twist rifling stabilizes modern 62-grain and heavier ammunition, making it flexible across typical 5.56 NATO loads.

Built by a US Government contractor to exacting standards, this barrel group features a chrome-lined bore applied over button rifling for durability and corrosion resistance. Every barrel undergoes high-pressure testing, magnetic particle inspection, and precision gauging before leaving the factory—no shortcuts, no surprises. The 4150 chrome moly steel construction is proven in military and law enforcement use and holds up to sustained firing and aggressive handling.

The assembly arrives pre-fitted with the slip ring, F-marked front sight base, and handguard cap already installed, so you can integrate it into your upper receiver without extra machining or fitting work. The barrel is chamber-marked 5.56x45mm NATO and carries the mil-spec rib for drop-in compatibility with standard AR-15 uppers. If you're building a compact 5.56 rifle or upgrading an existing platform with a proven, inspected barrel, this Brownells group takes the guesswork out of the process.