Colt M4/M4A1 Replacement Barrel Assembly 14.5In

If you're running an M4A1-style AR-15 carbine or building one from the ground up, a genuine Colt M4/M4A1 replacement barrel assembly gives you the same mil-spec foundation that Colt built for the U.S. military. This 14.5-inch barrel assembly is the complete package—barrel, extension, nut, and front-sight tower all together—so you can drop it onto your lower and get to the range without hunting down individual parts. Colt's expertise in direct-impingement rifle design is baked into every detail, from the chamber and rifling to the gas system tuning.

The barrel is chambered in 5.56 NATO and features six-groove rifling with a 1:7-inch twist rate, a time-tested combination that handles everything from 55-grain varmint loads to heavier 77-grain match rounds. The M4-style feed ramps ensure reliable chambering, and the chrome-lined bore resists corrosion—a critical feature if your rifle sees hard use or less-than-ideal storage conditions. The carbine-length gas system delivers the handling characteristics M4 shooters expect: a compact profile with reasonable recoil impulse.

The muzzle is threaded 1/2"-28 TPI, so you can mount suppressors, flash hiders, or muzzle brakes to suit your mission. Whether you're outfitting a new build, replacing a worn-out barrel, or upgrading a rifle you've inherited, this Colt assembly spares you the gunsmithing and headspace guessing—it's engineered to work.

Key Features

• Complete barrel assembly—no additional parts required for installation
• 5.56 NATO chambering with six-groove, 1:7-inch rifling
• M4-style feed ramps for reliable feeding
• Chrome-lined bore resists corrosion in field conditions
• Carbine-length gas system optimized for 14.5-inch barrel
• 1/2"-28 TPI threaded muzzle for suppressors and muzzle devices
• Includes barrel nut, front-sight tower, post, and sling swivel
• Genuine Colt military-specification design and production

Specifications

Frequently Asked Questions

Will this barrel assembly fit my AR-15 build?

Yes, if your AR-15 lower accepts a mil-spec carbine-length gas system and standard 1/2"-28 threaded muzzle. The Colt assembly is dimensioned to mil-spec, so it works with standard uppers and lowers. The included barrel nut, extension, and front-sight tower make installation straightforward for anyone comfortable with basic AR assembly.

What ammunition works best in this barrel?

The 1:7-inch twist rate and 5.56 NATO chamber handle a wide range of loads. It stabilizes heavier bullets like 77-grain match rounds as well as standard 55 to 62-grain service ammunition. Use commercially loaded 5.56 NATO or compatible reloads; do not use 7.62×39 or other non-NATO cartridges.

Is the barrel chrome-lined inside?

Yes. The bore is chrome-lined, which resists corrosion and extends barrel life under regular use and in humid or field storage conditions.

Can I attach a suppressor or muzzle device?

Yes. The muzzle is threaded 1/2"-28 TPI, the standard mil-spec threading for AR-15 barrels. You can install any commercial suppressor, flash hider, or muzzle brake with that threading.