The Colt LE6921CK Complete Upper Receiver Assembly is a factory Colt 14.5 inch 5.56 NATO / .223 Remington upper receiver assembly for compatible AR-15 / M4 pattern lower receivers. It gives builders a Colt M4-style upper with a chrome lined 14.5 inch barrel, fixed front sight base, A2 flash hider, bolt carrier group, and charging handle.

This complete upper is based on the Colt 6921 / M4-style configuration and is intended for shooters who want a factory Colt upper receiver assembly rather than a parts-bin build. The LE6921CK is a strong choice for M4-style clone builds, Colt carbine projects, spare upper assemblies, and hard-use AR builds where Colt factory pedigree matters.

Factory Colt 14.5 Inch Upper: The LE6921CK uses a 14.5 inch barrel chambered in 5.56 NATO. The M4-style barrel configuration, fixed front sight base, A2 flash hider, bolt carrier group, and charging handle make this a complete upper receiver assembly ready to pair with a compatible complete lower receiver.

M4-Style Barrel and Sight Setup: This upper follows the classic M4 pattern with a fixed front sight base, bayonet lug, handguard assembly, and A2-style flash hider. It is a strong fit for customers wanting a traditional Colt M4 upper rather than a free-float modern rail configuration.

Complete Upper Receiver Assembly: This product is a complete upper receiver assembly, not a complete rifle. When paired with a compatible complete AR-15 lower receiver, this upper can form a complete rifle, provided the final firearm configuration complies with all federal, state, and local laws.

Important 14.5 Inch Barrel / NFA Note: A 14.5 inch barrel is shorter than the standard 16 inch rifle barrel length. Installing this upper on a rifle lower without a permanently attached muzzle device that brings the barrel to at least 16 inches may create a short-barreled rifle regulated under the National Firearms Act. Confirm all federal, state, and local laws before purchase, assembly, transfer, or use.

Fitment Note: Confirm lower receiver compatibility, buffer system, gas system, barrel length requirements, muzzle device permanence if needed, headspace, optic or rear sight selection, magazine compatibility, and ammunition compatibility before installation or live fire.

Related Gear: Browse the AR-15 Store, shop compatible AR-15 lower parts, view muzzle devices, or pair this upper with compatible 5.56 NATO and .223 Remington ammunition.