Built on CMMG’s new-for-2016 ANVIL receivers that combine the strength of their MUTANT mid-size platform with their patented POWERBOLT technology, the MkW-15 XBE .458 SOCOM is a rugged and reliable piece. Our evaluation rifle was the mid-priced MkW-15 XBE .458 SOCOM ($1,949.95), but multiple other configurations are also available.

The CMMG RKM15 15-inch handguard shrouds the majority of the 16.1-inch barrel and gives you both, Keymod attachment points at 3, 6 and 9 o’clock and a top Picatinny strip along its entire length. Not visible is the is the SLR adjustable gas block hidden beneath. A Larue Q.D. LT-FUG forward grip, set of Samson Quick Flip backup iron sights and Blue Force Gear Padded Vicker’s Sling were used throughout testing.

Features common to all the rifles include Anvil mid-size receivers machined from billet 7075-T6 aluminum, a 16.1-inch (12.5-inch in the pistol variants), medium contour, 416 stainless steel, SBN barrels rifled at a 1:14” twist rate, a CMMG SV muzzle brake threaded 5/8” x  32 TPI and a CMMG RKM15 1-piece machined aluminum handguard with full-length Picatinny top-rail and M-Lok slots everywhere else.

The unique MkW lower receiver’s mag well readily accepts all standard AR-15/M16 magazines. The rifle ships with one CMMG-modified LANCER L5-AWM 30-round 5.56 NATO magazine, and as such can still hold 30 rounds of 5.56 NATO ammunition. The magazine has been modified to function properly with 10 rounds of .458 SOCOM  ammo, but will physically hold 11 rounds if forced.

The heaviest grain weight tested—SBR’s 350-gr. FMJ load—also proved the most precise at 100-yards, turning in this 0.78-inch three-shot group. Other loads tested (all pictured here) also produced admirable results, with performance that left nothing to complain about. With no shortage of factory-available ammo to choose from, finding the right load for the task at hand is a non-issue with the .458 cartridge.

One of the more innovative features of this rifle is its gas system. While using  standard gas tubes, all MkW XBEs come equipped with an Sentry 7 Set Screw Adjustable Gas Block that allows quick and easy gas pressure adjustment to ensure proper functioning with the wide range of available bullet weights (140 to 500 grains). Empty weight of the rifle is a reasonably-light 7.5-pounds.

For testing we mounted a Nikon Black Force 1000 1-4x24mm riflescope ($399.95) in a Larue Tactical 30mm Q.D. mount. Testing ammo consisted of Black Butterfly 300-gr. Barnes TSX hollowpoints, SBR 300-gr. Lehigh Defense Xtreme Penetrators, Polycase 200-gr. copper-polymer ARX Interceptors and SBR 350-gr. FMJs. From the 100-yard bench, the Anvil produced some very respectable results. All ammunition proved capable of producing at least one sub 1.75-inch three-shot group, but the Anvil seemed to show a distinct preference for the 350-gr. SBR load, keeping most of downrange performance within an inch center-to-center, and proding a best group of 0.78-inches. As one might expect, recoil energy increased alongside grain weight, with the lightest of the loads—the 200-gr. ARX—producing around 7.62x39mm felt recoil, and the heavy 350-gr. SBR approaching 12-ga. shotgun levels.

See it at your firearms retailer, or for more information contact CMMG, Inc., Dept. OT; Tel.: (660) 248-2293; Web: www.cmmginc.com