Leveraging their proprietary POWERBOLT technology found on the CMMG MUTANT, CMMG is now offering a rifle chambered in 458 SOCOM. The CMMG MkW ANVIL, is an Ar-15 patterned rifle that features an adjustable gas system, and a mid sized receiver that falls in between the Ar-15 and the Ar-10 in regards to size. The POWERBOLT was initially used on the 7.62 x 39 CMMG MUTANT, and was  designed to accommodate the 7.62 x 39 cartridge. In the past companies would take a standard Ar-15 bolt and machine the bolt face to accept the 7.62 x 39 round. This process would leave very little metal on the bolt face, and the lugs would prematurely crack within several thousand rounds. A typical bolt should last around 10,000 rounds. The CMMG MkW ANVIL feeds from standard Ar-15 magazines, and comes in several configurations and price points.



The 7.62 x39 round compared to the massive .458 SOCOM.


CMMG MkW ANVIL chambered in .458 SOCOM. The MkW feeds from a standard Ar-15 magazine.


The CMMG MkW ANVIL is also available as a Short Barrelled Rifle.


Key Specs of the basic MkW ANVIL include;

BARREL: 16.1” 1:14 Twist, Medium Taper 416SS SBN Barrel
MUZZLE: CMMG SV Brake, Threaded 5/8 – 32
FURNITURE: A2 Pistol Grip, M4 carbine stock with 6-pos mil-spec receiver extension
RECEIVERS: Billet 7075-T6 AL, Mid-Size MUTANT Platform
TRIGGER: CMMG Single Stage Mil-Spec style trigger
GAS PORT LOCATION: Carbine with SLR adjustable gas block

Please note other models include enhanced triggers as well as Magpul furniture.

Thomas Gomez

Thomas Gomez currently resides in the mountains of central New Mexico. He has an M.B.A, an Ar-15/M16/M4 armorer certification from Specialized Armament Warehouse as well as a Glock armorer certification. Aside from writing for The Firearm Blog he works as a Clinical Analyst for a large Hospital. He spends his free time farming, ranching, hiking, fly-fishing and hunting in the beautiful forests and prairies of New Mexico. He can be reached at


  • Corwin Bos

    You might want to go take a look at the 458 Socom forums to get some info on some of what you wrote and get in touch with Tony Rumore from Tromix. The bolts hold up just fine as people have fired 1000’s of rounds using Tromix’s bolt with no issues. Its a bunch of BS that has been spread around by CMMG to make their rifle appear better. Also, CMMG is not using the true 458 Socom reamer unless something has changed in the last couple of months, so effectively they are ripping off someone elses design because they dont want to pay money. And yes, there is a difference between the Tromix reamer and the bastardized crap CMMG and anyone else not using the Tromix reamer are selling.