The Rosco K9 11.5-inch Patrol Length AR Barrel in 5.56 NATO (ROSCO Manufacturing part no. K9-115-HY-DUFFY-556-7-PT) is a bare AR-platform barrel from ROSCO Manufacturing‘s K9 line, built at a patrol-length 11.5 inches for compact carbine and pistol builds. It is chambered in 5.56 NATO with a 1:7 twist rate, a common combination for stabilizing heavier bullet weights through a shorter barrel. As a bare barrel component, it is an ordinary Title I part; because it is under the federal 16-inch rifle minimum, it needs to go on a pistol-configured lower or a properly registered short-barreled rifle rather than an unregistered rifle-configured build.

Key Specifications

• Chambered in 5.56 NATO for standard AR-15 platform compatibility.
• A 1:7 twist rate stabilizes heavier 5.56/.223 bullet weights.
• An 11.5-inch patrol length barrel, part of Rosco’s K9 line built for compact builds.
• Machined from 416R stainless steel with a nitride finish for corrosion resistance and durability.
• Threaded 1/2×28 at the muzzle for compensators, brakes, or suppressor mounts.
• Built around Rosco’s proprietary patrol-length gas system, tuned smoother than a carbine-length system and more reliable than a mid-length system.
• Cut with an updated target crown for improved harmonics and accuracy.

Frequently Asked Questions

Can I buy this barrel without a tax stamp? Yes, an 11.5-inch bare barrel is an ordinary Title I part. It only requires NFA registration if installed on a shouldered, rifle-configured lower without prior ATF approval, so it belongs on a pistol build or a properly registered SBR.

What twist rate does this barrel use? A 1:7 twist, which stabilizes heavier 5.56/.223 bullet weights well.

Buy the Rosco K9 11.5-inch Patrol Length AR Barrel, 5.56 NATO

Order it from our Lubbock, Texas gun shop for fast, direct shipping and get your compact AR build moving. Browse more AR barrels to compare lengths and profiles.