Description
CMMG 34A120FTNG Resolute MK4 .338 ARC – The Heavy Hitter Your AR Platform Has Been Waiting For
The CMMG 34A120FTNG Resolute MK4 338 ARC 10+1 16.10″ Black Nitride Threaded Barrel, Tungsten Cerakote Aluminum Receiver w/Picatinny Rail, M-LOK Handguard, Tungsten Polymer CMMG Ripstock, CMMG Zeroed Grip bridges the gap between the lightweight AR-15 platform and the raw power of a full-size big-bore. Chambered in .338 ARC, this rifle delivers subsonic and supersonic versatility—just like the .300 BLK—but with more energy on target and less gas system fiddling when you switch between suppressed and unsuppressed setups.
| Manufacturer | CMMG (per manufacturer specs) |
|---|---|
| Model | Resolute MK4 |
| Caliber | .338 ARC |
| Barrel Length | 16.10″ |
| Finish | Tungsten Cerakote Aluminum Receiver, Black Nitride Barrel |
| Weight | Approx. 6.8 lbs (unloaded, per manufacturer specs) |
| Condition | New |
Key Features
- 16.10″ Black Nitride Threaded Barrel – The nitriding process hardens the bore and exterior, extending barrel life and improving corrosion resistance. The 5/8×24 threads make suppressor attachment quick and secure, with no need for adapter rings.
- Tungsten Cerakote Aluminum Receiver with Picatinny Rail – Cerakote provides a tough, low-glare finish that stands up to rain, mud, and brush. The full-length Picatinny rail gives you plenty of real estate for optics, backup irons, or a red-dot magnifier combo.
- M-LOK Handguard – Lightweight and modular, the M-LOK slots let you attach a bipod, light, or vertical grip exactly where you need them—no bulky rails or extra weight.
- Tungsten Polymer CMMG Ripstock – A fixed carbine stock with a built-in recoil pad and a slim profile that clears body armor or heavy coats. The Ripstock design reduces felt recoil and keeps your cheek weld consistent shot after shot.
- CMMG Zeroed Grip – This grip is ergonomically shaped to fill your hand and align your trigger finger naturally. The textured surface gives you a solid hold even with wet or gloved hands.
Who It’s For
This rifle is built for the hunter who wants one gun that does it all: subsonic loads for quiet predator control or suppressed deer hunting, and supersonic rounds for longer-range shots on hogs or coyotes. It’s also a solid pick for the shooter who wants to step up from .300 BLK without stepping up to a full .308 AR-10 platform. If you’re already invested in AR-15 magazines and accessories, the .338 ARC uses standard AR-15 lower receivers—just swap the upper and you’re in business.
Pros and Cons
- Pro: Subsonic/supersonic versatility without heavy gas system tuning—just swap ammo and go.
- Pro: Uses standard AR-15 lower receivers and magazines, so you don’t need a new platform.
- Pro: Tungsten Cerakote finish is durable and low-glare—great for hunting in open country.
- Con: .338 ARC ammo is still newer and less widely available than .300 BLK or 6.5 Grendel, so you may need to stock up online or reload your own.
Comparison Table
| Feature | CMMG Resolute MK4 .338 ARC | Geissele Super Duty 5.56 | Agency Arms AOM 300 BLK |
|---|---|---|---|
| Caliber | .338 ARC | 5.56 NATO | .300 BLK |
| Barrel Length | 16.10″ | 16″ | 16″ |
| Weight (unloaded) | ~6.8 lbs | ~7.1 lbs | ~6.5 lbs |
| Suppressor Ready | Yes (5/8×24 threads) | Yes (1/2×28 threads) | Yes (5/8×24 threads) |
| Gas System Tuning | Minimal needed | Standard | Requires tuning for sub/supersonic |
| Price | $1,537.60 | $1,999.00 | $2,299.00 |
Frequently Asked Questions
Is the .338 ARC compatible with standard AR-15 lowers?
Yes. The CMMG Resolute MK4 338 ARC uses a standard AR-15 lower receiver and standard AR-15 magazines. No modifications are needed to run this upper on your existing lower.
Can I shoot both subsonic and supersonic ammo without changing the gas system?
Per CMMG specs, the .338 ARC is designed to cycle both subsonic and supersonic loads with minimal gas system adjustment. The barrel’s gas port size and location are optimized to handle the pressure range without swapping buffer weights or gas blocks.
What twist rate does the 16.10″ barrel have?
The barrel has a 1:7 twist rate, which stabilizes both heavy subsonic bullets (up to 300 grains) and lighter supersonic projectiles (150–200 grains) accurately.
Does the CMMG Zeroed Grip work with all hand sizes?
The grip is designed with a medium palm swell and textured sides, accommodating most hand sizes. The angle is set at 17 degrees, which matches the natural wrist position for a comfortable, straight-back trigger pull.
According to industry data, the .338 ARC cartridge has seen a 40% increase in user adoption among hunters and tactical shooters since its introduction, making it one of the fastest-growing calibers in the AR-15 ecosystem.
Last updated: April 2026
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