16” 5.56 / 223 1:7 carbine ultralight Ar15 pencil barrel

Super light 1lb barrel, .625 gas block diameter, carbine gas, 5.56 nato 1:7 chamber, 4150cmv steel

16″ 5.56 NATO 1:7 Carbine Ultralight Pencil Barrel — 4150CMV (RBC)

Build a lightning-fast AR-15 with this ultralight 16″ carbine pencil barrel from RBC. Weighing approximately 1 lb, this barrel is optimized for shooters who prioritize handling, maneuverability, and quick target transitions without sacrificing quality or durability. Constructed from heat-treated 4150CMV steel, this barrel delivers robust service life in a lightweight package.

• Caliber / Chamber: 5.56 NATO (compatible with 223 also)
• Twist Rate: 1:7 — stabilizes heavier, longer bullets often used in modern 5.56 loads
• Length: 16″ carbine
• Profile: Ultralight pencil — minimal mass for fast handling
• Material: 4150CMV steel — durable and proven for service barrels
• Gas System: Carbine gas
• Gas Block Diameter: .625″ (.625 gas block)
• Threads: 1/2-28 standard muzzle threads
• Compatibility: M16 / AR-15 upper receivers (verify extension & indexing per your installer)

Why choose this ultralight pencil barrel?

This barrel is perfect for shooters who want the feel and agility of a sub-compact rifle while retaining the ballistics and legal length advantages of a 16″ barrel. The 1:7 twist favors heavier projectiles (62gr and up) commonly used in modern 5.56 loads and some specialized varmint or match applications. With a carbine gas system and .625 gas block diameter, the gas timing is tuned for reliable cycling in lightweight configurations.

Order this barrel as a standalone upgrade, or pair it with our upper assembly services and matched parts kit for a ready-to-go upper. Browse our barrels • Upper parts kits • Contact us for custom builds.

Specifications

Notes & installation

• This listing is for barrel only. Upper assembly, installation, and headspacing are available as add-on services — see our Services page or add an upper parts kit & BCG during checkout.