Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

Gun Reviews Mark Miller Rifles

What’s in your chamber? The hybrid CMMG Resolute .458 SOCOM is designed to bring 600 grains of punch to the hunt. Whether you’re defending your family or looking to bring home the bacon (and all the other cuts), the .458 SOCOM RESOLUTE keeps going when you need it most.

CMMG’s RESOLUTE is the perfect choice for this big caliber. The .458 SOCOM achieves optimum ballistic performance in the 16-inch barrel providing great balance, accuracy, and maneuverability.

The RESOLUTE lineup is available in three tiers: RESOLUTE 100, RESOLUTE 200 and RESOLUTE 300, each customized to give you the features you want at the price you need.

The CMMG 458 Socom is a beefy rifle. The hybrid receivers, the .458 barrel, and the .458 bolt are fat where it counts. At only 7 lbs 4oz, the Resolute is quite comfortable to shoot.

The CMMG Mid-sized hybrid receivers are NOT compatible with standard AR-15 (CMMG Mk4) or .308 WIN (CMMG Mk3) uppers.

Resolute™ 200 .458 SOCOM

  • BARREL: 16.1″, 1:14 twist, Medium Taper, 416SS
  • MUZZLE: CMMG SV Brake, threaded 5/8-32
  • GAS PORT: Carbine Length with SLR Adjustable Gas Block
  • RECEIVER: Billet 7075-T6 AL Mid Size upper, Billet 7075-T6 AL Lower
  • HANDGUARD: CMMG RML15 M-Lok handguard
  • FINISH: Hard Coat Anodized Receivers and Hand Guard (Upgrade to Cerakote)
  • CHARGING HANDLE: CMMG Standard Mid-Size
  • BUTTSTOCK: CMMG RipStock with 6 Position Enhanced Receiver Extension and Ambi Sling Plate
  • TRIGGER: CMMG Single stage mil-spec style trigger
  • TRIGGER GUARD: Integrated Into Lower
  • MAGAZINE: Ten round CMMG Modified Lancer Magazine
  • WEIGHT: 7 lbs 4oz (unloaded)
  • LENGTH: 33.3″(stock collapsed)
  • Ships with two CMMG Modified Lancer Magazines
Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

A MAGPUL pistol grip and a thin profile KeyMod handguard allow you to get your hand forward for control. Felt recoil is something like 12 gauge birdshot.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

The mighty SV muzzle brake tames the .458 to feel like 12 gauge birdshot.

The Resolute lower receiver is generous for rapid reloads. It will accept any AR 15 magazine. The Lancer magazines provided have metal feed lips and have been modified to increase reliability with the .458 SOCOM. I used several magazines from favorite brands. Mission First Tactical magazines, MAGPUL, and GI aluminum mags. All of them worked great.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

The Resolute sports a KeyMod Handguard and a CMMG RipStock with 6 Position Enhanced Receiver Extension and Ambi Sling Plate.

The .458 SOCOM cartridge was designed to be compatible with the AR platform. This included the buffer, buffer spring, GI magazines, many aftermarket .223/5.56 magazines, and magazine well.

In a .223/5.56 AR magazine, cartridges are staggered in a double stack. With the larger .458 SOCOM, rounds single stack with no modification to the standard AR magazine feed lips or followers. A 20-round 5.56mm NATO magazine can hold seven .458 SOCOM rounds and a 30-round 5.56mm NATO magazine can hold ten .458 SOCOM rounds.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

Groups at 100 yards were a consistent 4MOA with both subsonic and supersonic loads. There was a small zero shift.

I was able to shoot two hundred rounds in three different .458 SOCOM loads. The SBR Ammunition 300gr Solid Brass and 500gr Round nose subsonic loads as well as the ARX 200gr Interceptor.

Each of these loads cycled well. The groups were very consistent at 100 yards. The best 5 round groups measured just under 4 inches.

The .458 SOCOM (11.63×40mm) promises the ballistics of the legendary .45-70 in the AR platform rifle. The .458 launches 250 to 600 grain .458 caliber bullets with manageable recoil.

Building an AR in .458 SOCOM requires a .458 specific bolt and barrel. The ejection port opening of the upper receiver must be extended to allow clearance for the larger cartridge.

The .458 SOCOM feeds from most standard unmodified 5.56 AR magazines. CMMG provides Lancer L5 AWM magazines. The Lancer 20 round 5.56 magazine holds seven SOCOM rounds and the 30 round 5.56 magazine will hold nine.

The .458 round has a reputation for breaking guns.  It has been said  “The .458 round is well suited for stopping an intruder. In your neighbor’s house.  Behind a refrigerator.” Immensely powerful, yes it is, but CMMG has built a rifle that runs it.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

For hunting medium to large game, 250 grain– 400-grain bullets are very effective. The 300-grain (19 g) round offers a supersonic muzzle velocity of 1,900 ft/s (580 m/s) and 2,405 ft⋅lbs (3,261 J), similar to a light .45-70 but with a much smaller case.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

The 458 SOCOM cartridge

The Resolute’s 1-14 twist barrel is a great choice to use with a suppressor. The SOCOM will launch 500- 600-grain bullets at subsonic velocities for suppressed or tactical use.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

Nikon FORCE1000 1-4x24mm Riflescope. with the SPEEDFORCE Illuminated reticle.Nikon’s Black Force 1000 1-4X IL is the perfect pairing for the CMMG  .458 SOCOM. The 1 X 4 power scope allows quick transition from close range to distant targets and back.

The SPEEDFORCE Illuminated reticle uses a double horseshoe design for making precise shots out to mid-ranges without over-magnifying your target and provides moving-target leads with quick target acquisition. Side-mounted illumination adjustment lets you select from 10 different intensity settings to precisely meet ambient lighting conditions.

Big Bullets, Big Ballistics: The CMMG Resolute .458 SOCOM

Nikon FORCE1000 1-4x24mm SPEEDFORCE Illuminated reticle

This BLACK FORCE 1000 Riflescope is O-ring sealed, nitrogen purged, and durably constructed to be waterproof, fog proof, and shockproof. All glass surfaces on this scope are multi-coated to maximize light transmission.
Nikon’s Black Force1000 1-4X is an affordable solution for both tactical shooters and hunters with an MSRP at less than $400.


Color: Black
Magnification: 1 – 4 x
Objective Lens Diameter: 24 mm
Tube Diameter: 30 mm
Reticle: Illuminated Speedforce
Illumination Color: Red
Eye Relief: 4.1 – 3.8 in
Exit pupil: 6 – 24 mm
Adjustment Type: MOA
Adjustment Click Value: 0.25 MOA
Adjustment Range: 350 MOA
Field of View, Linear: 11.01 – 27.2 ft at 100 yds
Parallax: 100 yds
Optical Coating: Anti-Reflective/Multi-Layer Coated
Battery Type: CR2032
Water Resistance Level: Waterproof
Shockproof: Yes
Fogproof: Yes
Length: 4.72 in
Finish: Type III Hardcoat Anodized


  • SPEEDFORCE Illuminated Reticle with versatile double horseshoe design draws the eye to the center of the viewing field for fast targeting.
  • Glass-etched Illuminated Reticle is located in Second Focal Plane.
  • Side-mounted Illumination control features 10 intensity settings and powers down after 1 hour of non-operation.
  • True 1x magnification and 4x zoom for both-eyes-open engagement matched with long-range aiming precision.
  • Full Multilayer Coatings On All Glass Surfaces – multiple layers of anti-reflective coating maximize light transmission, brightness and contrast.
  • Optical System lead- and arsenic-free glass used for all lenses.
  • Generous, Consistent Eye Relief for fast sighting with a full sight picture.
  • Quick Focus Eyepiece with smooth-turn rubberized ring allows crisp reticle focus.
  • Capped Windage & Elevation Turrets for total sighting confidence under the toughest conditions.
  • Spring-Loaded Instant-Zero Reset Turrets engraved for maximum readability and internals provide precise, repeatable corrections while zeroing.
  • Waterproof, Fogproof O-ring sealed, nitrogen purged for total reliability.
  • Shockproof construction.
  • Side-mounted illumination adjustment features 10 intensity settings for use in all lighting conditions, including bright sunlight.
  • Built with aircraft grade 6061-T6 aluminum alloy 30mm main body tube and finished with Type-III hard anodizing surface finish for maximum ruggedness and long-term durability.

The CMMG Resolute is the perfect rifle to tame the biggest AR caliber, the .458 SOCOM. It combines awesome power and advanced design into a manageable package.

MSRP $2024.95

Photos by Mark Miller

For more information visit CMMG website.

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  • Evan July 8, 2019, 4:18 pm

    So wait, why should I get this over buying (or building) an upper that is compatible with lowers I already have?

    What extra performance do I get for that extra money?

  • Jay July 8, 2019, 9:56 am

    I prefer the 450 Bushmaster. Bullet weights being the same the 450 can push higher velocities and many times it can push higher than listed velocities as the gun is capable of more than listed without signs of being over pressured. To each their own and I know CMMG makes some quality products and stands behind their product’s!

  • Jon July 8, 2019, 8:01 am

    Luv the Big Bore AR’s!
    I built a 450 Bushmaster using a Bear Creek Arsenal side charging upper and 16″ barrel.
    I chose the 450 because it is less expensive to shoot.

    • Rane July 8, 2019, 9:32 am

      The 450 BM is a great caliber. It often out powers the 458. The reason I chose 458 over 450 was because I shoot suppressed and wanted the option to shoot 500-600 grain pills subsonic. That and for us reloaders the fact the 458 headspaces on the shoulder instead of the mouth of the cartridge makes life easier. The 458 also doesn’t need a long barrel 12” is all you really need to reach the sweet spot. That’s another reason why it’s popular with the suppressor crowd. Don’t be ashamed of your 450, that thing is a certified bass ass!

  • Rane July 8, 2019, 5:04 am

    CMMG has been making some really interesting stuff lately. I’ve built several 458’s and this one is awesome. The ONLY thing I would change would be the trigger. I prefer a lighter trigger for hunting. I build my 458’s with billet receivers, 16” barrels with carbine gas, SLR adj blocks, 1:14 twist, and high end BCG’s. CMMG has already done that and they did a better job making the receivers. I would have never built mine if this gun were around 5 years ago.This caliber was intended for the AR15, but like some other AR calibers they benefit from custom sized receivers. The 225gr Lehigh Bullets in this caliber are great for hunting. I’m able to get 2,200 fps with my hand loads. Very accurate too.

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