The upper features a premium, cold hammer forged barrel made from mil-spec 4150 chrome-moly vanadium steel that is black nitride finished for durability and corrosion resistance, while both the bolt and carrier are subjected to a magnetic particle inspection (MPI) test to ensure a strong, defect-free product. The upper receiver is a flat-top design for compatibility with Picatinny-style optic mounts, and comes complete with M4 feed ramps, laser-engraved rail indexing marks, mil-spec bolt carrier group, charging handle, brass deflector and ejection port door.
The barrel has been finished inside and out with an advanced salt bath nitriding treatment that bonds with the metal on a molecular level. Also referred to as Melonite, this finish produces an extremely hard, slick surface on steel that resists carbon adhesion and increases corrosion resistance, extending a barrel's service life by reducing the friction produced inside the bore upon firing for a net decrease in bore surface wear over time. Nitriding converts the barrel steel's surface without any build-up, retaining all of the benefits of traditional chrome lining without suffering the accuracy degradation commonly encountered due to uneven application of chrome inside the barrel's bore. The end result is a barrel that's capable of producing accuracy on par with a match stainless steel tube, while also exhibiting the longevity and resilience of a chrome lined, mil-spec barrel.
The upper's MFR 12.0 Modular Rail Handguard provides multiple options for adding accessories, while also free floating the barrel for greater accuracy potential. With the exception of the full length, uninterrupted top rail, the MFR's slim and smooth exterior offers more user comfort than a quad-rail design, yet also allows for the installation of modular rail sections where desired for accessories. The 18" barrel features Ambush Firearm's signature Strength 2 Weight (S2W) contour for the perfect balance of barrel weight and stiffness, while the 6.8mm SPC Spec II chamber is suitable for use with either standard or high pressure 6.8mm Remington SPC factory ammunition.
- Upper Receiver: Flat-Top w/Case Deflector, No Forward Assist
- Barrel Length: 18"
- Barrel Contour: Strength to Weight (S2W)
- Barrel Material: 4150 Chrome Moly Vanadium, Cold Hammer Forged
- Muzzle Thread Pattern: 5/8"-24
- Chrome Lined: No
- Barrel Finish: Melonite / Black Nitride
- Twist Rate: 1 in 11"
- Chamber: 6.8x43mm SPC II
- M4 Feed Ramps: Yes
- Muzzle Device: None, Thread Protector
- Gas System Length: Mid
- Gas Block Diameter: 0.750"
- Handguard: MFR 12.0 Modular Rail, Free Float
- Sights: None
- Extras: Low Profile Gas Block, 3 Modular Rail Sections, Shotgun-Style Forend
- Weight: 4 lbs, 8.0 oz