CMMG Mk4 .300 AAC Blackout SBR, 8 in Nitrided 4140 CrMo Barrel, RKM7 KeyMod, Magpul STR, BCMGUNFIGHTER Mod 4, AAC 51T Brake
This NFA item (SBR) from CMMG is a compact, purpose-built .300 AAC Blackout rifle featuring an 8 in nitrided 4140 chrome-moly steel barrel and the RKM7 7 in KeyMod free-float handguard. It comes outfitted with Magpul furniture, a BCM BCMGUNFIGHTER Mod 4 charging handle, and an AAC Blackout Muzzle Brake 51T suppressor mount. Forged, hard-anodized receivers with a flat-top, T-marked upper round out a well-appointed AR-15 platform designed for the .300 BLK cartridge.
Condition
Overall Condition: Very good condition, showing only light, superficial signs of prior handling or use.
Bore Condition: Excellent - Clean, mirror finish, no signs of wear.
Rifling: Excellent - Sharp lands and grooves.
Specific Condition Notes: The exterior shows a few minor, superficial scratches and small scuffs from light handling.
What’s Included
- 1x 30-round Magpul PMAG polymer AR-15 magazine
- Magpul STR carbine stock (installed)
- Magpul MOE-K pistol grip (installed)
- CMMG RKM7 7 in free-float KeyMod handguard (installed)
- AAC Blackout 51T ratcheting QD suppressor-mount muzzle brake (installed)
- BCM BCMGUNFIGHTER Mod 4 extended-latch charging handle (installed)
The 8 in nitrided 4140 CrMo steel barrel is optimized for .300 AAC Blackout, with a low-profile gas block under the free-float handguard and a threaded muzzle. The AAC Blackout Muzzle Brake 51T suppressor mount is installed, providing a robust brake that also serves as a QD suppressor interface.
The CMMG RKM7 7 in KeyMod Free Float Handguard keeps weight forward to a minimum while offering ample mounting real estate. The flat-top upper has T-markings on the Picatinny rail and includes a forward assist, case deflector, and ejection-port cover. The upper shows an "A" forging mark; the lower is marked MK4 with "CMMG INC FAYETTE, MO USA."
Magpul furniture includes the STR 6-position stock with QD sling socket and the MOE-K pistol grip, delivering a compact, controllable setup. A BCM BCMGUNFIGHTER Mod 4 charging handle with an extended latch aids in fast, positive manipulation. Length of pull is approximately 10.5-14 inches.
This AR-15 platform rifle uses a direct impingement action and forged aluminum receivers with a hard-anodized finish. It accepts STANAG-pattern magazines and has a stated capacity of 30+1. The manual safety selector is standard. Country of origin is the USA. This is a NFA item (SBR).