CMMG Mk4 S 5.56mm Semi-Automatic Rifle (55A66E1)

CMMG Mk4 S 5.56mm Semi-Automatic Rifle (55A66E1)


CMMG-55A66E1

How To Buy A Firearm

We will price match any currently priced, in stock item. In some rare instances we may not be able to match a price but will do all that we can to give you the best deal possible. (We cannot match the price if it is under our cost) Please call store at 1.800.486.7497 to check availability for immediate pickup. Please review the Terms and Conditions HERE.

Type: Rifles


  • Perfect rifle for the tree stand or target range
  • Utilizes an 18" 416 stainless steel medium taper barrel chambered in 5.56x45mm NATO and CMMG's RKM14 KeyMod hand guard
  • KeyMod hand guard is ready to accept any number of the sling mounts, bi-pods and other KeyMod compatible accessories making the ultimate in versatility and modularity
  • Includes a magazine and CMMG's lifetime quality guarantee
  Caliber     5.56mm  
  Barrel     18"”, 1:7 twist, medium taper, 416SS, bead blasted finish  
  Muzzle     A2 comp., threaded 1/2-28  
  Hand Guard     CMMG RKM14 KeyMod hand guard  
  Furniture     A2 pistol grip, M4 butt stock with 6-pos mil-spec receiver extension  
  Receivers     Forged 7075-T6 AL M4 type upper, AR15 type lower  
  Trigger     Single stage mil-spec style trigger  
  Gas Port Location     Rifle  
  Length, in     34" (stock collapsed)  
  Weight, lbs     6.7 (unloaded)