CMMG 5.7x28mm 5-inch Barrel & BCG Kit (57DBC33)

Description

This CMMG kit includes a 5-inch barrel and matching bolt carrier group chambered in 5.7x28mm. It is designed for drop-in installation into a mil-spec AR-15 upper and is built around CMMG’s Radial Delayed Blowback operating system. The kit is supplied in a black SBN finish and is intended for compact AR pistol or SBR configurations. It works with CMMG Mk57 lower receivers and can work with standard Mk4/AR-15 lowers when used with CMMG 5.7 conversion magazines.

Key Specifications

• The chambering is 5.7 x 28 mm.
• The barrel length is 5 inches.
• The kit includes a barrel and bolt carrier group (BCG).
• The barrel steel/blank is specified as 4140CM.
• The finish is SBN.
• Designed for drop-in installation into a mil-spec AR-15 upper.
• Operates using CMMG’s Radial Delayed Blowback system.
• Compatible with CMMG Mk57 lowers and standard Mk4/AR-15 lowers when using CMMG 5.7 conversion magazines.

This kit provides a straightforward path to a compact 5.7x28mm AR configuration, delivering a reduced-mass BCG and the functional benefits of CMMG’s Radial Delayed Blowback design. It is a practical option for builders seeking a compact, modern operating system for AR pistols or SBR projects.