Dirty Bird 16" 5.56 M4 Carbine Phosphate/Chrome-Lined AR-15 Barrel w/ F-Marked FSB - D264

The Dirty Bird 16″ 5.56 M4 Carbine barrel is the backbone of a retro build. Machined from CrMoV steel with a chrome-lined bore and chamber, it’s built for the guys who shoot their rifles hard and would rather clean less and run more. Chrome lining shrugs off corrosion, extends throat life, and makes carbon come out easy after a long range day — the same reason the military has specified it for decades.

The 5.56 NATO chamber runs everything from cheap 55gr blasting ammo to duty-grade 62gr and .223 Remington without complaint, and the 1:7 twist stabilizes heavy loads all the way up to 77gr match if you want to stretch it out. Carbine-length gas keeps the rifle running dirty, cold, or suppressed. The M4 profile with phosphate-coated M4 feed ramp extension drops straight into any standard M4-cut upper.

Where this one earns its keep is the front sight. It ships with a pinned F-marked front sight base, which is the taller FSB spec’d for flat-top upper receivers. Run it under a detachable carry handle or with a standard-height rear BUIS and your sights line up where they’re supposed to — no shimming, no holding low, no “why is my front post buried in the rear aperture.”

It also ships with the handguard cap, delta ring assembly, and front sling swivel already installed, so you’re not chasing down small parts to finish the front end — pair it with a set of standard M4 drop-in handguards and the build comes together fast. Thread it, torque it, headspace it, and you’ve got a rifle that will outlast most of what’s bolted around it.

Backed by the Dirty Bird Lifetime Guarantee

FEATURES

• 16″ barrel length
• Chrome-lined bore and chamber for extended barrel life and easier cleaning
• Pinned F-marked front sight base — correct sight height for flat-top uppers
• Ships with handguard cap, delta ring assembly, and sling swivel — ready for standard M4 two-piece drop-in handguards
• CrMoV (chrome moly vanadium) steel construction
• Manganese phosphate exterior finish
• 5.56 NATO chamber — safely runs 5.56 NATO and .223 Rem
• 1:7 twist stabilizes 55gr through 77gr projectiles
• Carbine-length gas system
• M4 profile with phosphate-coated M4 feed ramp extension
• 1/2×28 threaded muzzle accepts standard AR-15 muzzle devices

IN THE BOX

• 16″ 5.56 M4 profile barrel
• Pinned F-marked front sight base and assembly
• Handguard cap
• Delta ring assembly
• Front sling swivel