5.56 NATO remains the backbone of the AR-15 platform, and few upgrades influence accuracy, reliability, and longevity as dramatically as a quality barrel. At Arm or Ally you’ll find button- and cut-rifled 4150 CMV and 416R stainless options in 10.3″, 12.5″, 14.5″, 16″, and 18″ lengths—each profiled to balance heat management and weight. Whether you’re building a duty-grade carbine, a recce-style SPR, or a suppressor-ready SBR, we stock the gas system you need: carbine, mid-length, or rifle, all finished with M4 extensions, polished feed ramps, and ½-28 threads. Popular twists include 1:7 for 77-grain OTM loads and 1:8 for all-purpose versatility. Chrome-lined and QPQ nitride treatments fight throat erosion, while our stainless match barrels add a recessed target crown and guaranteed sub-MOA groups with quality ammunition. Pair any of these tubes with our low-profile gas blocks, nitride bolt-carrier groups, and free-float handguards to maximize the inherent accuracy baked into modern 5.56 barrels.