AR-15 6mm ARC 20" Hexagon Fluted Stainless Steel Upper Assembly – 15" M-LOK

6mm ARC Upper: Specs & Features

The Moriarti AR-15 6mm ARC 20" Hexagon Fluted Stainless Steel Upper Assembly combines match-grade barrel construction with a precision-oriented configuration for the AR-15 platform. Chambered in 6mm ARC, this upper features a 20-inch, hand-lapped 416R stainless steel barrel with distinctive hexagon fluting, a medium profile, and a 1:7.5 twist rate.

Designed for sporting and precision target applications, the 6mm ARC cartridge offers an efficient combination of velocity, ballistic performance, and compatibility with the AR-15 platform. The match-grade stainless steel barrel features a natural stainless finish, M4 feed ramps, and 5/8x24 muzzle threading.

The rifle-length gas system incorporates a .750-inch low-profile steel gas block with a nitride finish and a stainless steel rifle-length gas tube.

The upper assembly features a forged 7075-T6 aluminum A3 flat-top receiver with a black hardcoat anodized finish, installed forward assist, and dust cover. A 15-inch free-floating M-LOK handguard, constructed from aircraft-quality aluminum with a black hardcoat anodized finish, provides a continuous top Picatinny rail and accessory mounting positions.

The combination of the hexagon-fluted stainless barrel and black M-LOK handguard creates a distinctive appearance while maintaining the functionality of a full-length AR-15 upper assembly.

Bolt carrier group and charging handle are not included. Both are available as optional selections.

Key Features

• 6mm ARC chambering

• 20" match-grade 416R stainless steel barrel

• Natural stainless steel barrel finish

• Distinctive hexagon barrel fluting

• Medium barrel profile

• Hand-lapped barrel

• 1:7.5 barrel twist rate

• Rifle-length gas system

• .750" low-profile steel gas block with nitride finish

• Stainless steel rifle-length gas tube

• 5/8x24 muzzle threads

• M4 feed ramps

• Forged 7075-T6 aluminum A3 flat-top upper receiver

• Black hardcoat anodized receiver finish

• Installed forward assist and dust cover

• 15" free-floating M-LOK handguard

• Aircraft-quality aluminum handguard construction

• Continuous top Picatinny rail

• Optional BCG and charging handle

• Compatible with mil-spec AR-15 lower receivers

Specifications

Package Includes

• Assembled Moriarti AR-15 6mm ARC 20" upper receiver assembly

• Installed 20" hexagon-fluted 416R stainless steel barrel

• Forged 7075-T6 A3 flat-top upper receiver

• Installed forward assist and dust cover

• Installed 15" free-floating M-LOK handguard

• Rifle-length stainless steel gas tube

• .750" low-profile steel gas block

Not Included Unless Selected: Bolt carrier group and charging handle.

FAQ

What barrel does this 6mm ARC upper feature?

A 20-inch, hand-lapped, match-grade 416R stainless steel barrel with hexagon fluting, a medium profile, and 1:7.5 twist rate.

Does the barrel have a nitride finish?

No. The barrel features a natural stainless steel finish. The steel gas block has a nitride finish.

Will this upper fit a standard AR-15 lower receiver?

The upper is designed for compatible mil-spec AR-15-pattern lower receivers.

What bolt carrier group and magazines are required?

A compatible 6mm ARC / 6.5 Grendel-type bolt and 6mm ARC-compatible magazines are required. A standard 5.56 NATO bolt is not compatible.

What gas system does this upper use?

A rifle-length gas system with a .750-inch low-profile steel gas block and stainless steel gas tube.

What handguard is installed?

A 15-inch free-floating aluminum M-LOK handguard with a black hardcoat anodized finish and continuous top Picatinny rail.

Are the bolt carrier group and charging handle included?

No. Both components are available as optional selections.

Product Image Notice

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Related: 6mm ARC uppers · all AR-15 upper assemblies