CMMG 57D0476 5.7x28mm Barrel and BCG Kit, 16.1"

CMMG 5.7x28mm Barrel and BCG Kit

This complete barrel and bolt carrier group kit represents a thoughtful approach to building a modern, efficient AR-platform carbine in 5.7x28mm. The 16.1" barrel length provides a practical balance between velocity and handling characteristics.

Operating System Advantage

The standout feature is CMMG's patented Radial Delayed Blowback system. This is not your typical direct blowback design. The key benefits include:

• Reduced bolt carrier weight compared to standard blowback systems
• Noticeably less felt recoil without compromising reliability
• Last round bolt hold open functionality preserved
• Smoother cycling and improved shooter control

Compatibility and Assembly

The kit is engineered for Mk4/mil-spec AR15 uppers and works seamlessly with either a CMMG Mk57 lower receiver or standard Mk4/AR15 mil-spec lower receiver. When using a standard lower, you'll need CMMG 5.7 AR Conversion Magazines to ensure proper function.

Practical Applications

Whether you're building a carbine, AR pistol, or short-barreled rifle, this kit provides everything needed for a complete upper assembly. The 5.7x28mm cartridge offers mild recoil, reduced noise signature, and excellent accuracy at typical defensive distances.

This is a complete solution for shooters seeking to explore an alternative caliber within the familiar AR-platform ecosystem.