CMMG Mk4 .300 AAC Blackout AR-15 Rifle, 16 in Barrel, Free-Float M-LOK, Tan Finish, 30+1
This CMMG Mk4 is a .300 AAC Blackout AR-15 pattern rifle with a 16 inch threaded barrel, a free-float M-LOK aluminum handguard, and a tan/earth-tone finish on the receivers and handguard. It features AR-15 pattern controls with a forward assist, ejection port cover, and brass deflector, plus a left-side safety selector. A flat-top upper receiver with Picatinny rail and a low-profile gas block provide a clean, modern setup. It comes with one 30-round Magpul PMAG marked for 300 BLK.
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 Notes: The exterior shows scattered light scratches and small blemishes consistent with prior handling.
What’s Included
- CMMG Mk4 .300 AAC Blackout rifle
- One 30-round Magpul PMAG (polymer) marked 300 BLK / 7.62x35
- M-LOK bolt-on Picatinny rail section installed at 12 o'clock on the handguard
Chambered in .300 AAC Blackout (7.62x35mm), this Mk4 uses a direct impingement, semi-automatic operating system and a low-profile gas block. The 16 inch barrel is threaded and fitted with an A2-style flash hider.
The rifle is built around AR-15 pattern controls, including a right-side magazine release, forward assist, ejection port cover, and brass deflector. A left-side-only manual safety with SAFE/SEMI markings is standard.
The free-float M-LOK aluminum handguard offers modern attachment capability and includes a bolt-on Picatinny rail section at the 12 o'clock position. The flat-top upper receiver has its own Picatinny rail; the handguard’s top rail is a separate bolt-on section rather than a continuous/monolithic rail, and there are no sights installed.
A collapsible 6-position stock on a carbine receiver extension provides an adjustable length of pull from 10 to 13.5 inches and includes a rear sling loop. The rifle is finished in a tan/earth-tone on the receivers and handguard, and it wears a CMMG-branded textured polymer pistol grip.
Made in the USA, this configuration carries a 30+1 maximum capacity and ships with a 30-round Magpul PMAG specifically marked for 300 BLK.