Personal defense calibers like 5.7x28mm have become a big thing in the last few years and if you’re looking for PDW ballistics and the classic style and balance of a carbine then you’re in luck. Combine this RESOLUTE Upper Group with either our Mk57 Lower or a standard AR15 lower group and CMMG’s 5.7 AR Conversion Magazines and you’ll be ready to hit the range! Available in six different Cerakote finishes all CMMG Upper Groups come complete with bolt carrier group and ZEROED accessories including: – ZEROED AR15 Polymer Dust Cover – ZEROED AR15 Ambi Charging Handle – ZEROED Muzzle Brake 5.56mm – Platform: Mk4 Mk57 – Caliber: 5.7x28mm – Operating System: Radial Delayed Blowback – Barrel Length: 16.1 – Barrel Twist: 1:9 – Barrel Contour: MT – Barrel Material: 4140CM SBN – Muzzle Device: CMMG ZEROED Muzzle Brake – Muzzle Thread: 1/2 x 28 – Upper Receiver: Billet 6061 T6 Aluminum – Hand Guard: CMMG EML15 M-LOK – Finish: Cerakote Standard – Charging Handle: CMMG ZEROED Ambi – Weight: 4.0 lbs – Length: 25.3