CMMG Resolute MK4 .338 ARC 10+1 16.10″ Threaded

About this product

What is the CMMG Resolute MK4 .338 ARC 10+1 16.10″ Threaded? It is a purpose-built short-barreled AR-15 platform chambered for the modern .338 Advanced Rifle Cartridge, designed for shooters who need extended range and terminal ballistics from a compact system without constant re-tuning. This configuration uses a gas system specifically tailored for .338 ARC pressures to maintain reliable function across both supersonic and subsonic loads, which is critical when switching between suppressed hunting and unsuppressed target applications. Built with Ironclad Armory's direct-spec approach, it eliminates the guesswork from a cartridge that many AR builders struggle to implement correctly.

What is the CMMG Resolute MK4 .338 ARC used for?

The primary use is as a compact, semi-auto capable medium-game and long-range target rifle where bolt-action platforms like the Stevens 334 are too slow for follow-up shots. I consider this the ideal platform for hunting in terrain where shots may exceed 500 yards but rapid engagement of multiple targets, like in predator control, is a possibility. Its 16.10-inch barrel and integral rail system also make it an excellent candidate for conversion to a Title II weapon if you intend to file a Form 1 for a short-barreled rifle, as the barrel is already pre-threaded 5/8-24 for a direct-mount suppressor.

How does the CMMG Resolute MK4 compare to building a .338 ARC AR myself?

The Resolute MK4 is superior to a home-built upper for reliability, specifically in gas-port diameter and buffer-weight matching, which are the two most common failure points for this cartridge. Where an amateur builder might use a standard .30-caliber gas block and a rifle buffer, CMMG has engineered this system around a .750" journal with a calibrated port and includes a proprietary H2 buffer to manage bolt-carrier velocity with heavier bullets. You will spend more upfront vs sourcing parts individually, but you avoid the $200-$300 in function-testing ammunition and potential gunsmithing fees to correct short-stroking or over-gassing.

What does it weigh and what are the dimensions?

The firearm weighs 6.20 pounds empty and measures 37.30 inches in overall length, giving it a balance point approximately 5 inches forward of the magazine well. With a fully loaded 10-round .338 ARC magazine inserted, the total weight climbs to approximately 7.1 pounds, which is noticeably heavier than a 5.56 NATO AR-15 of similar dimensions but provides a stability advantage for off-hand shooting. The 16.10-inch cold-hammer-forged barrel features a 1:8" twist rate, which is the optimal stabilization for bullet weights from 200 to 300 grains common to this caliber.

Who is this NOT for?

This rifle is not for the budget-conscious plinker or someone seeking their first AR-pattern rifle. The .338 ARC cartridge itself costs roughly $2.50 per round for factory supersonic loads, making practice prohibitively expensive compared to the .223 Remington or .308 Winchester chamberings found on more common platforms like the Stevens 334. Furthermore, if you have no intention of using a suppressor or engaging targets beyond 400 yards, the ballistic advantages of the .338 ARC are wasted, and you would be better served by a standard .308 AR-10 pattern rifle with cheaper and more widely available ammunition.

What's in the box?

You receive the complete rifle with the CMMG Ripstock installed, one 10-round Magpul PMAG .338 AC magazine, a CMMG Zeroed grip, the factory-installed linear compensator, and a single-point sling attachment point. Ironclad Armory also includes a chamber flag and a small toolkit containing the correct Allen key for adjusting the Ripstock's cheek riser, which is a detail many manufacturers omit. Note that the box does not include iron sights, optics, a sling, or a case—these are considered user-specific accessories and must be purchased separately.

Is the CMMG Resolute MK4 worth it at $1554.99?

At this price point, the Resolute MK4 represents strong value for a turn-key .338 ARC system, coming in approximately $400-$600 less than a comparable custom-built upper and lower from a specialty shop. You are paying for a validated, range-tested system that will cycle a wider variety of loads out of the box than a part-for-part assembly, which is critical for a cartridge still in its adoption phase. Compare this to the value proposition of our Stevens 334 in .308 Win, which is a competent bolt-action for less than half the price but sacrifices semi-automatic capability and modularity for pure cost savings.