CMMG Mk4 AR-15 SBR, 5.56mm NATO, 12.5" Nitrided Barrel, RKM11 11" KeyMod, AAC 51T Brakeout, BCM Mod 4, Magpul STR
This registered short-barreled rifle from CMMG is a Mk4-series AR-15 in 5.56mm NATO, built around a 12.5" nitrided 4140 chrome-moly steel barrel and a free-float RKM11 11" KeyMod handguard with a continuous top rail. It is configured with an AAC Brakeout 2.0 51T suppressor-mount muzzle device, a BCM BCMGUNFIGHTER Mod 4 charging handle, and Magpul furniture including the STR stock. This is an NFA item (SBR).
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Overall Condition: Excellent - Clean, mirror finish, no signs of wear.
Bore Rifling: Excellent Rifling - Sharp lands and grooves.
Specific Condition Details: This firearm is in great shape. There are some minor and superficial scratches and blemishes present. The bore is clean and shiny.
What’s Included
- CMMG Mk4 5.56mm NATO registered SBR (as described)
- 1x 30-round Magpul PMAG (5.56x45, polymer)
Built on the AR-15 platform, this Mk4 uses a semi-automatic, direct-impingement operating system and a flat-top upper equipped with a forward assist and ejection-port cover. The upper and handguard provide a continuous top rail for mounting sights or accessories as needed.
The 12.5" barrel is made from 4140 chrome-moly steel and treated with a salt-bath nitride (QPQ) finish. It is threaded and factory-fitted with an AAC Brakeout 2.0 muzzle device that serves as a 51T suppressor mount.
The free-float CMMG RKM11 11" KeyMod aluminum handguard offers mounting flexibility while keeping weight forward in check. No iron sights are included.
Controls and furniture are well-appointed: the BCM BCMGUNFIGHTER Mod 4 charging handle with a medium latch provides positive purchase, while the Magpul STR collapsible stock adds dual sealed storage tubes and ambidextrous QD sling sockets. A Magpul pistol grip rounds out the setup.
Capacity is 30+1 with the included Magpul PMAG. This rifle is made in the USA and is a registered short-barreled rifle that transfers as an NFA item.