The Colt M4 5.56mm Carbine SBR (Model CR6921) is an authentic factory Short-Barreled Rifle produced by Colt. This model features the iconic 14.5-inch barrel with a pinned and welded muzzle device, making it a true SBR straight from the manufacturer. Built to the same high standards as Colt’s military M4 carbines, the CR6921 delivers the reliability, accuracy, and handling characteristics that have made the M4 platform the standard for military and law enforcement agencies worldwide.
Important Note: This is a factory-configured Short-Barreled Rifle (SBR). Ownership requires proper NFA registration with the ATF, payment of the $200 tax stamp, and compliance with all federal, state, and local laws.
Authentic Colt M4 Design
The Colt CR6921 is a direct descendant of the military M4 carbine. It features a 14.5-inch chrome-lined barrel with a 1:7 twist rate, optimized for the 5.56 NATO cartridge. The barrel is equipped with a pinned and welded muzzle device to meet overall length requirements while maintaining the compact profile that makes the M4 so effective in close-quarters and vehicle operations. The rifle uses a carbine-length gas system and comes with a standard M4 collapsible stock and carbine handguards.
The 14.5-inch barrel provides an excellent balance between velocity, maneuverability, and controllability, making the CR6921 highly effective for home defense, tactical applications, and professional use where a compact platform is required.
Key Features of the Colt M4 CR6921 SBR
- 14.5-Inch Barrel – Chrome-lined with 1:7 twist rate
- Factory SBR Configuration – Pinned and welded muzzle device
- 5.56 NATO / .223 Remington – Chambered in the most popular intermediate cartridge
- M4 Profile Barrel – Lightweight and proven design
- Carbine Length Gas System – Reliable cycling and smooth operation
- Collapsible Stock – 6-position adjustable stock for customized length of pull
- Model CR6921 – Official Colt factory part number
- UPC 098289023605 – Authentic Colt product
Why Choose the Colt M4 CR6921 SBR?
The Colt M4 CR6921 offers the performance and reliability of a genuine Colt military-style carbine in a compact SBR format. While many aftermarket SBRs are built from various components, the CR6921 is a complete factory-assembled rifle from Colt, ensuring consistent quality and proper headspacing. The 14.5-inch barrel provides better velocity and terminal performance than shorter 10.5" or 11.5" barrels while remaining significantly more maneuverable than a standard 16-inch carbine. Colt’s reputation for building some of the most reliable AR-platform rifles in the world makes the CR6921 a trusted choice for professionals and serious enthusiasts who want an authentic M4 experience in SBR form.
Technical Specifications
| Brand | Colt |
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| Model | M4 Carbine SBR |
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| Part Number | CR6921 |
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| Caliber | 5.56 NATO / .223 Remington |
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| Barrel Length | 14.5 Inches |
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| Barrel Type | Chrome-Lined, M4 Profile |
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| Twist Rate | 1:7 |
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| Gas System | Carbine Length |
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| Stock | 6-Position Collapsible |
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| Classification | Short-Barreled Rifle (SBR) |
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| UPC | 098289023605 |
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Ideal Applications
The Colt M4 CR6921 SBR is particularly well-suited for scenarios where a compact, highly maneuverable rifle is required. It excels in home defense applications where a shorter overall length is advantageous in confined spaces. Law enforcement and tactical teams often prefer 14.5-inch SBRs for vehicle operations and close-quarters work. The platform is also popular among competitive shooters in 3-Gun and tactical competitions where speed and handling are critical. Because it is a factory SBR, the CR6921 offers the peace of mind that comes with a complete, professionally assembled firearm from one of America’s most respected manufacturers. The 5.56 NATO chambering provides excellent terminal performance with widely available and affordable ammunition.
Experience authentic Colt quality and performance with the Colt M4 5.56mm SBR Carbine. Featuring a 14.5-inch barrel, factory SBR configuration, and the legendary reliability of the M4 platform, the Model CR6921 delivers professional-grade performance in a compact package. UPC 098289023605.
