Dirty Bird 14.5" 5.56 M4 Carbine Phosphate/Chrome-Lined AR-15 Barrel w/ F-Marked FSB

The Dirty Bird 14.5" 5.56 M4 Carbine barrel is the real thing - the exact length the M4 has used since it was adopted, and still the sweet spot between handling and velocity. You give up very little downrange compared to a 16", and you get back a rifle that's noticeably quicker to move, easier to run in tight spaces, and better balanced with a can on the end. Machined from CrMoV steel with a chrome-lined bore and chamber, it's built for volume. Chrome lining resists corrosion, protects the throat through long strings of fire, and makes cleanup after a hard weekend a lot less miserable - the reason it's been the military standard for decades. The 5.56 NATO chamber runs 55gr plinking ammo, 62gr duty loads, and .223 Rem interchangeably, and the 1:7 twist holds everything up through 77gr match. Carbine-length gas is the factory-correct pairing at 14.5" and keeps the gun cycling when it's filthy, freezing, or suppressed. The M4 profile with phosphate-coated M4 feed ramp extension drops into any standard M4-cut upper. Up front is a pinned F-marked front sight base - the taller FSB spec'd for flat-top upper receivers. Pair it with a detachable carry handle or a standard-height rear BUIS and your sights line up correctly with no shimming and no holding low. It ships with the handguard cap, delta ring assembly, and front sling swivel already installed, so it takes standard carbine-length two-piece drop-in handguards right out of the box. All NFA/ATF rules apply. Backed by the Dirty Bird lifetime guarantee. FEATURES 14.5" barrel length - true M4 spec Pin and weld a muzzle device to reach 16"+ for a non-NFA rifle build, or run as an SBR or pistol 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 carbine-length 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 1/2x28 threaded muzzle accepts standard AR-15 muzzle devices and suppressor mounts IN THE BOX 14.5" 5.56 M4 profile barrel Pinned F-marked front sight base and assembly Handguard cap Delta ring assembly Front sling swivel