CMMG Endeavor Mk4 5.56mm 18" Rifle - Armor Black Finish

The CMMG Endeavor Mk4 5.56mm 18" rifle is a purpose-built AR15 designed for shooters who want genuine long-range capability without compromise. Built on CMMG's proven Mk4 platform and chambered in the versatile 5.56x45mm cartridge, this rifle pairs a nitride-finished 416 stainless steel barrel with a 1:7 twist rate to deliver the ballistic performance serious marksmen expect. Whether you're extending your effective range at the precision rifle range or hunting with a cartridge that still dominates the modern sporting rifle world, the Endeavor Mk4 delivers the accuracy and customization potential to get the job done.

The backbone of the Endeavor Mk4 is its billet upper receiver and forged lower receiver, both machined from premium aluminum alloys. This rifle ships with a complete collection of CMMG's ZEROED components—including an ambidextrous charging handle, drop-in trigger, and modular safety selector—so you get a cohesive, tuned platform out of the box. The Magpul MOE rifle stock provides a comfortable, adjustable cheek weld, while the CMMG ZEROED muzzle brake helps manage recoil and muzzle rise during rapid strings.

Modularity is baked in. The EML 15 handguard features M-LOK attachment slots at the cardinal positions plus integrated Picatinny rail sections, giving you plenty of real estate to build the optics and accessory package that fits your mission. Because it's built on the Mk4 platform and uses standard AR15 internals, you can customize virtually every component to match your shooting style. At 7 lbs and 37.8" overall, the Endeavor Mk4 strikes a practical balance between maneuverability and shootability—light enough to carry, substantial enough to run consistently.

The rifle arrives with a Magpul 30-round PMAG and all the parts you need to get to the range immediately. CMMG's attention to detail—from the billet receiver quality to the choice of barrel material and gas system—reflects their commitment to rifles that perform when it counts.

Key Features

• 18-inch 416 stainless steel barrel with 1:7 twist for 5.56x45mm performance and accuracy
• CMMG ZEROED muzzle brake reduces recoil and muzzle rise
• Billet upper receiver and forged lower receiver for durability and precision
• EML 15 handguard with M-LOK slots and integrated Picatinny rail sections for unlimited accessory mounting
• Ambidextrous CMMG ZEROED charging handle and safety selector for left and right-handed shooters
• Drop-in CMMG ZEROED trigger for improved trigger control
• Magpul MOE adjustable rifle stock for comfort and customization
• Fully compatible with standard AR15 components and upgrades
• Includes one 30-round Magpul PMAG

Specifications

Frequently Asked Questions

What does the 1:7 barrel twist rate mean for 5.56 ammo?

The 1:7 twist is optimized to stabilize a wide range of 5.56x45mm bullet weights, from standard 55-grain rounds to heavier projectiles. This versatility means you can run whatever 5.56 ammo is available or suits your mission without worrying about spin rate.

Can I swap out the stock, handguard, trigger, or other parts?

Yes. The Endeavor Mk4 is built on the standard AR15 platform, so it's fully compatible with any AR15-spec components. You can upgrade or customize virtually any part to build the rifle that matches your needs.

What's included with the rifle?

The Endeavor Mk4 ships with one 30-round Magpul PMAG and all the components you see listed in the specifications. It's ready to shoot once you acquire an optic and ammunition.

Is the muzzle brake removable?

The CMMG ZEROED muzzle brake is threaded with a 1/2 x 28 connection, which is the standard for 5.56mm ARs. You can replace it with another muzzle device that uses the same thread pitch if you prefer a different setup.