CMMG 5.7x28mm 8" Barrel & BCG Kit – Radial Delayed Blowback

5.7x28mm

CMMG 5.7x28mm 8" Barrel & BCG Kit | Radial Delayed Blowback

The CMMG 5.7x28mm 8" Barrel and BCG Kit combines the two core CMMG components for a compatible AR-platform 5.7x28mm configuration: an 8" 416 stainless steel barrel and CMMG's Radial Delayed Blowback BCG.

Unlike conventional straight-blowback systems that rely heavily on bolt mass, CMMG's patented Radial Delayed Blowback (RDB) system uses a rotating bolt design to delay the action and allows the system to operate with less reciprocating mass.

The barrel features an 8" medium-taper profile, 1:9 twist rate, 1/2x28 muzzle threads, and salt-bath nitride finish. Because this is a Radial Delayed Blowback configuration, there is no conventional AR-15 gas-port location or gas system.

8" 5.7x28mm Barrel Specifications

• Caliber: 5.7x28mm
• Barrel Length: 8"
• Twist Rate: 1:9
• Profile: Medium Taper
• Material: 416 Stainless Steel
• Muzzle Thread: 1/2x28
• Gas Port Location: N/A
• Finish: Salt Bath Nitride
• Operating System: CMMG Radial Delayed Blowback
• Kit Weight: 1 lb. 10 oz.

CMMG Radial Delayed Blowback BCG

The included bolt carrier group is engineered to work as part of CMMG's Radial Delayed Blowback system. Rather than treating the barrel and BCG as unrelated AR components, this kit provides the matched CMMG barrel-and-bolt system required for the RDB operating design.

Lower & Magazine Compatibility

The CMMG 5.7x28mm system has been offered in both Mk57 and Mk4/AR-15-style configurations. The 5.7x28mm CMMG platform can therefore support different magazine configurations depending on the receiver setup.

For the version you are selling, I would retain CMMG's stated compatibility language:

Designed for use with a CMMG Mk57 lower receiver or a compatible standard AR-15 lower when using CMMG 5.7 AR Conversion Magazines.

Customers should verify receiver and magazine compatibility for their specific configuration.

Does a CMMG 5.7x28 barrel and BCG kit use a standard AR-15 gas system?

No. CMMG's 5.7x28 Radial Delayed Blowback system does not use the conventional gas-operated system found on a standard 5.56 AR-15. The barrel therefore has no conventional gas-port location, and the included RDB bolt carrier group is an integral part of the operating system. CMMG's RDB design uses bolt rotation and carrier movement to delay opening rather than using barrel gas to cycle the action.

Product Highlights

CMMG | 5.7x28mm | 8" Barrel | 1:9 Twist | 416 Stainless Steel | Medium Taper | 1/2x28 Threads | Salt Bath Nitride | Radial Delayed Blowback | Barrel + BCG Kit | 1 lb. 10 oz.