Faxon Firearms 5.56X45 Nato 10.5'' 1-8 Pencil Bbl W/Pinned Gas Block Nitride

The Faxon Firearms 5.56x45 NATO 10.5" 1-8 pencil barrel with pinned gas block is a complete, ready-to-assemble upper receiver component built for shooters who want accuracy and reliability without the guesswork. This short-barrel rifle (SBR) or pistol upper combines a lightweight, stress-relieved barrel with a pre-pinned low-profile gas block—eliminating the most common point of failure in short-barrel builds. If you're assembling a compact AR-15 for close-quarters work, home defense, or a lightweight trainer, Faxon's no-nonsense engineering gets you shooting faster.

The 10.5" barrel comes finished in Nitride, a corrosion-resistant hardening process that protects against wear and the elements without adding significant weight. The pencil profile keeps the overall system lightweight—just 0.9 lbs—while the 1-in-8 twist rate stabilizes modern 5.56 ammunition across the velocity range you'll see from a short barrel. Faxon manufactures these barrels in-house from 4150 CMV steel, stress-relieving and air-gauge testing each one, then finishing with an 11-degree target crown for inherent accuracy. Every barrel is magnetic-particle inspected and individually checked for headspace to ensure consistency.

The included gas block is already pinned and seated on the barrel journal, with the pin and set screws in place. This pre-notched design—where Faxon drills corresponding holes in both the block and barrel—prevents the gas block from shifting or loosening under recoil, a common problem in short-barrel builds where dwell times are aggressive. The low-profile design won't interfere with most rail systems. The barrel extension is M4 compatible, the muzzle is threaded 1/2-28, and the 0.625" gas block diameter fits standard carbine gas systems.

Faxon barrels represent solid value for builders who want quality control and in-house manufacturing without boutique pricing. This is a purpose-built short-barrel component, not a compromise—pick one up if you're serious about a compact, accurate, reliable build.

Key Features

• Pre-pinned low-profile gas block eliminates loose gas block failures
• Lightweight pencil profile at 0.9 lbs
• 1-in-8 twist rate optimized for modern 5.56 ammunition across short-barrel velocities
• Nitride-finished 4150 CMV steel for corrosion resistance and durability
• Stress-relieved, air-gauge tested, and magnetic-particle inspected for consistency
• 11-degree target crown for inherent accuracy
• Individually headspace-checked before shipment
• M4 extension with 1/2-28 muzzle threading
• Includes gas block, pin, and set screws—ready to install

Specifications

Frequently Asked Questions

What is included with this barrel?

The barrel comes complete with a pre-pinned low-profile gas block, the gas block pin, and set screws. The gas block is hand-tightened to the barrel for shipping and ready to install into your upper receiver.

Is this barrel suitable for a short-barrel rifle (SBR) or pistol build?

Yes. The 10.5" length and carbine-length gas system are designed for compact AR-15 builds, including SBRs and pistol uppers. The 1-in-8 twist rate is appropriate for 5.56 ammunition across the velocity range typical of short barrels.

What is the advantage of a pinned gas block?

A pinned gas block (combined with set screws) prevents the gas block from shifting or loosening under recoil—a common failure point in short-barrel builds where cycling is aggressive. Faxon pre-notches the barrel journal and drills corresponding holes in the included gas block, so the pin is installed correctly from the factory.

What is the muzzle thread pattern, and what accessories can I attach?

The muzzle is threaded 1/2-28, a standard AR-15 pattern compatible with flash hiders, muzzle brakes, and suppressors designed for that specification.