The Colt Monolithic Carbine 14.5-inch SBR is a 5.56 NATO short-barreled rifle built around Colt’s patented one-piece monolithic upper receiver (Colt part no. LE6944). The upper runs a continuous MIL-SPEC rail from the rear of the receiver to the front sight position, which gives optics a repeatable mount that a two-piece upper and handguard cannot offer. The 14.5-inch barrel floats free of that rail for consistent accuracy, and Magpul MBUS folding sights are fitted. Colt ships it with two 20-round Colt magazines. It is the M4-length member of Colt’s monolithic family for a shooter who wants rigidity and reach in one compact rifle.

Key Specifications

• The chambering is 5.56 NATO, the cartridge the M4 platform was built around.
• Barrel length is 14.5 inches, the M4 dimension that balances velocity and handling.
• The upper is a one-piece monolithic receiver with a continuous MIL-SPEC top rail.
• The barrel is free floating, which removes rail pressure from the barrel for better accuracy.
• Two 20-round Colt magazines are included.
• Sights are Magpul MBUS folding sights, ready as backups under an optic.
• The action is semi-automatic, running Colt’s direct gas impingement system.
• The barrel is chrome lined, Colt’s standard for corrosion resistance and barrel life.
• The bolt is HP/MPI tested for safety and reliability.
• It accepts standard AR-15 pattern magazines beyond the two that ship with it.

Frequently Asked Questions

Do I need ATF approval to buy this? No. As of October 9, 2026, ATF no longer requires Form 4 approval, registration or a tax stamp for short-barreled rifles. It transfers on a Form 4473 with a background check through a Class 3 (SOT) dealer. State and local laws still apply. Taking an SBR across state lines still requires an approved ATF Form 5320.20.

How is a monolithic upper different from a standard AR upper? The receiver and rail are one forged piece with a continuous top rail, so there is no joint between receiver and handguard to shift an optic’s zero, and the barrel floats free.

How many magazines are included? Two 20-round Colt magazines.

Buy the Colt Monolithic Carbine 14.5-Inch SBR

As of October 9, 2026, this short-barreled rifle transfers on a Form 4473 with a background check at your Class 3 (SOT) dealer, with no Form 4 or tax stamp; state and local laws still apply. Order through Colt‘s AR rifles lineup and our Lubbock, Texas team will handle the transfer.