CMMG Upper Receiver Parts Kit Mk4 / Mk9

The
Ruger AR556, like its more expensive cousin the SR556, is packed with
features that fans of the Modern Sporting Rifle demand.
The
AR556 is direct impingement gas-operated with a 16-inch 1:8
hammer-forged barrel threaded 1/2×28. Also featured is a
windage-adjustable rear flip-up sight, a six-position telescoping
M4-style buttstock with a Mil-Spec buffer tube, M4 feed ramps, a
matte Type III hard coat oxide finish, enlarged trigger guard, a
chrome-plated bolt carrier, and an A2-style front post sight with
elevation adjustment, a bayonet lug and a Q/D attachment socket. This
rifle also comes with one 30-round Magpul PMAG.

Specifications:

Special Feature: Threaded Barrel Model
Weight: 6.5 lbs.
Rate-of-Twist: 1-in-8″
Sights: Adjustable Ruger Rapid Deploy
Additional Info: Flat Top M4 Design
Additional Info: Milled F-Height Gas Block
Additional Info: Improved Trigger Reach Grip