CMMG Resolute Mk4 5.7x28mm 16.1" Barrel Rifle - Armor Black Finish

The CMMG Resolute Mk4 5.7x28mm rifle splits the difference between a full-size carbine and a short-barreled platform, delivering a practical package for shooters who want AR modularity without overcommitting to traditional rifle dimensions. Built on the familiar Mk4 platform but chambered in the modern 5.7x28mm cartridge, the Resolute bridges the gap where pistols run out of steam and full-length rifles feel unwieldy. At 16.1 inches, the barrel stretches enough to unlock the velocity and range that make this round worth considering for personal defense or general-purpose use, while the overall length of 32.5 inches keeps the gun responsive in tight quarters.

What sets the Resolute apart is its commitment to the AR ecosystem. Instead of forcing proprietary magazines, CMMG engineered their 5.7x28mm line to feed from magazines that drop straight into a standard AR15 magwell. That means your existing gear works, your muscle memory transfers, and you're not locked into a single supplier. The radial delayed blowback operating system handles the diminutive 5.7x28mm round with the reliability you'd expect from CMMG's track record, while the 1:9 barrel twist is optimized for this cartridge's typical projectile weight range.

The gun ships with a complete suite of ZEROED components: ambi charging handle, ambi safety selector, ambidextrous sling plate, and a drop-in trigger. The EML15 handguard keeps weight down while offering M-LOK slots at the cardinal positions (12, 3, 6, and 9 o'clock) for mounting lights, rails, or other accessories. The RipStock provides a proven ergonomic platform, and the 6.4-pound weight won't wear you out over a long day. Armor Black Cerakote finish resists corrosion and keeps the gun looking businesslike.

Whether you're exploring a new cartridge or want a modern rifle that doesn't demand a dedicated ecosystem, the Resolute Mk4 in 5.7x28mm deserves a serious look.

Key Features

• 5.7x28mm chambering optimized for personal defense and general-purpose shooting
• CMMG 5.7x28mm magazines feed from standard AR15 magwells—full platform compatibility
• Radial delayed blowback operating system for reliable function
• Complete ZEROED component package: ambi charging handle, ambi safety, ambi sling plate, and drop-in trigger
• EML15 M-LOK handguard with slots at 12, 3, 6, and 9 o'clock for accessory mounting
• RipStock platform for comfortable, ergonomic shoulder support
• Billet 6061 T6 upper and forged 7075 T6 lower receiver for durability
• Armor Black Cerakote finish resists corrosion
• Lightweight at 6.4 lbs and compact at 32.5 inches overall length

Specifications

Frequently Asked Questions

Will this rifle work with my existing AR15 magazines?

No. The Resolute Mk4 uses CMMG's purpose-built 5.7x28mm magazines, but these magazines are designed to feed from standard AR15 magwells. So while you need dedicated 5.7x28mm mags, they drop in and work with conventional AR15 receivers and rifle architecture. The supplied magazine holds 32 rounds.

What is the 5.7x28mm cartridge good for?

The 5.7x28mm is a modern, low-recoil cartridge designed for personal defense and general-purpose shooting. It offers better velocity and range than a pistol round from a rifle-length barrel without the size or recoil of traditional rifle calibers. It's gaining popularity among shooters who want AR modularity paired with a lighter-shooting, lower-noise platform.

Is this rifle fully assembled and ready to shoot?

The product record does not specify the level of assembly or what comes in the box. Contact Bosque Outdoors directly for details on what is included and any assembly or function checks.

What accessories can I mount on the EML15 handguard?

The EML15 M-LOK handguard has attachment slots at the 12, 3, 6, and 9 o'clock positions, allowing you to install lights, vertical foregrips, rails, or other M-LOK-compatible accessories wherever you need them on the gun.