Moriarti AR-15 300 Blackout 14.5" Upper – 12" Slim M-LOK, Thread Protector

14.5" 300 Blackout Upper: Specs & Features

The Moriarti 14.5" 300 Blackout Upper Assembly delivers the versatility of 300 AAC Blackout in a longer-barrel AR-15 configuration. Designed for shooters seeking a premium 14.5 300 Blackout upper, this assembly provides an excellent platform for hunting, recreational shooting, and custom AR-15 projects.

The 14.5-inch 300 BLK barrel provides additional barrel length for shooters who prioritize supersonic performance while retaining the versatility that makes 300 Blackout popular. Built with quality AR-15 components for dependable cycling, accuracy, and durability, this 300 Blackout upper is compatible with Mil-Spec AR-15 lower receivers and standard AR-15 components where applicable.

Key Features:

• Cartridge: 300 Blackout – Ideal for both suppressed and unsuppressed shooting.
• Barrel Length: 14.5" – Balanced for maneuverability and performance.
• Barrel Profile: Medium Profile – Ideal for precision and durability.
• Barrel Material: 4150 Chrome Moly Steel – Known for strength and longevity.
• Barrel Finish: Black Nitride – Enhances durability, corrosion resistance, and performance.
• Twist Rate: 1:7 – Perfect for stabilizing a wide range of bullet weights.
• Gas System: Pistol-Length Gas System – Optimized for reliability and smoother cycling.
• Muzzle Device: Thread Protector – Protects the threads for future muzzle device installation.
• Upper Receiver: 7075-T6 Forged Aluminum – Strong, lightweight, and built to last.
• Handguard: 12" Slim M-LOK Free Float Rail – Slim, ergonomic, and ideal for attaching accessories.
• Thread Pitch: 5/8x24 – Standard for many AR-15 barrels and muzzle devices.
• M4 Feedramps – Ensures smoother feeding and reliability.
• Gas Block Size: .750 – Compatible with a wide range of gas blocks.

Specifications:

• Overall Length: 14.5 in
• Twist Rate: 1:7
• Barrel Material: 4150V Chrome Moly Steel
• Barrel Finish: Black Nitride
• Gas System: Pistol Length
• Muzzle Device: Thread Protector (Nitride Coated)
• Handguard Length: 12 in
• Handguard Type: Slim M-LOK Free Float
• Gas Block Diameter: .750 in
• Receiver Material: 7075-T6 Forged Aluminum
• Receiver Finish: Black Hardcoat Anodized

Package Contents:

• Moriarti AR-15 300 Blackout 14.5" Slim M-LOK Upper Assembly
• 12" M-LOK Free Float Handguard
• Thread Protector (Nitride Coated)

Is a 14.5-inch barrel good for 300 Blackout?

Yes. While 300 Blackout is well known for performing efficiently from short barrels, a 14.5-inch 300 Blackout upper can be an excellent choice for shooters who primarily use supersonic ammunition and want additional velocity from a longer barrel. Recent enthusiast discussion also shows 14.5" 300 BLK being used specifically for hunting-oriented configurations.

Note:
This upper assembly does not come with a Bolt Carrier Group (BCG) or Charging Handle. These can be purchased separately. The mlok handguard design may vary based on stock availability, but all components maintain excellent quality.

FAQ

Can 300 Blackout ammo be mixed up with 5.56?

Keep them separate. A 300 BLK round can chamber in a 5.56 rifle and firing it can destroy the gun, so mark your 300 BLK magazines and uppers clearly.

Is a bolt carrier group included?

No. Add a standard AR-15/5.56 bolt carrier group; it is available as an add-on on this page.

Is it suppressor ready?

Yes. The barrel is threaded 5/8x24, the standard pitch for .30 caliber muzzle devices and suppressor mounts.

Related: 300 Blackout AR-15 uppers · 300 Blackout suppressors · 5.56 NATO vs 300 Blackout

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