The 16.1” 5.7x28mm Barrel and BCG Kit is just the thing for building a carbine length AR in 5.7x28mm using CMMG’s patented Radial Delayed Blowback operating system. Unlike typical direct blowback systems, Radial Delayed Blowback not only reduces the weight in your BCG but it results in less felt recoil than a straight blowback system without sacrificing key features like last round bolt hold open. CMMG’s 5.7x28mm Barrel and Bolt Kits are designed to be assembled into a Mk4/mil-spec AR15 upper and work with either a CMMG Mk57 lower receiver or Mk4/AR15 mil-spec lower receiver (when using CMMG 5.7 AR Conversion Magazines).

Specifications 

CMMG 57D88C3
AR-15 Barrel and Bolt Carrier Group
5.7x28mm FN
16.1″ 4140CM Barrel
Threaded
Patented Radial Delayed Blowback
CMMG Lifetime Quality Guarantee
Salt Bath Nitride Finish
Matte Black

Includes:
Barrel
Bolt Carrier Group