Faxon Firearms Pencil Duty Series 5.56 Nato 10.5" Black Nitride 4150 Cmv

The Faxon Firearms Pencil Duty Series 5.56 NATO 10.5" barrel is built for shooters who refuse to compromise between weight and durability. This short-barreled rifle (SBR) or pistol upper component uses a narrow profile—hence "pencil"—to shed unnecessary ounces without sacrificing the robust 4150 CMV steel construction that defines Faxon's reputation. Whether you're building a lightweight patrol rifle, a nimble home-defense upper, or an ultra-portable truck gun, this barrel delivers the rigidity and reliability you need in a package that won't bog down your platform.

Manufactured at Faxon's ISO-certified facility, each Pencil Duty barrel undergoes magnetic particle inspection to guarantee consistent quality and internal integrity. The black Nitride finish resists wear and corrosion in the field, and the 1-in-8" twist rate stabilizes the full spectrum of 5.56 loads—from 55-grain varmint rounds to heavier match and barrier-blind ammunition. The M4 feedramps ensure reliable chambering and extraction, while the ½-inch by 28 TPI muzzle threads accept standard suppressors, flash hiders, and brakes.

This 10.5" barrel pairs with carbine- or mid-length gas tubes and accepts low-profile gas blocks 1" or shorter, making it ideal for builds where space and sight-line access matter. It will not accommodate standard-length front sight blocks, so plan your gas-block selection accordingly. If you're assembling a lightweight, maneuverable AR-15 upper without padding the weight budget, the Faxon Pencil Duty barrel is the no-nonsense choice.

Key Features

• Pencil profile saves weight while maintaining 4150 CMV steel strength and rigidity
• Black Nitride finish for enhanced wear and corrosion resistance
• 1-in-8" twist rate handles the full range of common 5.56 NATO loads
• M4 feedramps for reliable feeding and extraction
• ½" x 28 TPI muzzle threads for suppressors and muzzle devices
• Accepts low-profile gas blocks 1" or shorter
• Magnetic particle inspected for quality assurance
• Manufactured at ISO-certified facility

Specifications

Frequently Asked Questions

Will this barrel work with my standard front sight block?

No. The Pencil Duty barrel will not accept standard-length front sight blocks. You'll need to use a low-profile gas block that is 1" or shorter in length.

What gas tube length does this barrel use?

This barrel is designed for carbine-length or mid-length gas systems. Confirm your upper receiver's gas tube specification before ordering.

Can I use a suppressor on this barrel?

Yes. The ½" x 28 TPI muzzle threads are standard and will accept most .223/5.56 suppressors, flash hiders, and muzzle brakes.

Is this barrel suitable for heavy or subsonic ammunition?

The 1-in-8" twist rate is rated to stabilize the full range of common 5.56 NATO loadings, including heavier match-grade and barrier-blind rounds. Consult Faxon's twist-rate guidance if you plan to shoot ammunition outside standard commercial specifications.