At 7.5 inches with a pistol-length gas system and 1:7 twist, this Combat Armory 5.56 barrel is configured for a short-barreled AR pistol build. The 1:7 twist rate stabilizes a wide range of 5.56 NATO projectiles including heavier 62–77 gr loads, and the pistol gas system provides the shorter dwell time appropriate for a sub-10-inch barrel. 41V50 Chrome Moly Vanadium — Parkerized Finish This barrel is machined from 41V50 chrome moly vanadium steel — a high-strength alloy offering good toughness — and finished with a Parkerized (manganese phosphate) coating for corrosion resistance and matte appearance. Browse the full 5.56 and AR-15 parts lineup at shop Combat Armory. Full Specifications Caliber: 5.56 NATO / .223 Remington. Length: 7.5 inches. Twist rate: 1:7 RH. Thread pitch: 1/2×28. Gas system: pistol length. Gas seat diameter: 0.750″. Feed ramps: M4 style. Finish: Parkerized. Material: 41V50 chrome moly vanadium. Combat Armory AR Barrel — Specifications Caliber 5.56 NATO / .223 Remington Material 41V50 Chrome Moly Vanadium Length 7.5 inches Thread Pitch 1/2×28 Twist Rate 1:7 RH Gas System Pistol Length Finish Parkerized Manufacturer Combat Armory Who This Barrel Is For AR pistol and SBR builders who need a mil-spec 5.56 barrel in the 7.5-inch pistol-gas configuration. Drops into any mil-spec AR-15 upper receiver. Non-serialized; no FFL required — ships to your door. Pair with AR-15/AR9 parts or shop complete upper kits. What gas system does this barrel use? Pistol-length gas — the gas port is positioned for the shorter dwell time required by barrels under 10 inches. Does this need an FFL? No. This is a non-serialized barrel and ships directly to your door without an FFL transfer.