AR-15 Line

AR-15 .300 AAC Blackout 10.5" Pistol Builder Kit | M-LOK, SBA3 Brace, USA Made – Moriarti Armaments

Build your next AR-15 with the Moriarti Armaments AR-15 .300 AAC Blackout 10.5" Pistol Builder Kit. Designed for reliability, compact performance, and customization, this kit includes nearly everything needed to complete your AR-15 pistol build—excluding the 80% stripped lower receiver.

Featuring a 10.5-inch heavy-profile barrel, free-float M-LOK handguard, and SBA3 adjustable stabilizing brace, this builder kit is ideal for compact .300 Blackout builds. The pistol-length gas system is optimized for the 10.5" barrel configuration, while the forged 7075-T6 upper receiver and Mil-Spec components provide dependable performance.

Whether you're assembling your first AR-15 or upgrading an existing project, this USA-made kit delivers the quality and compatibility builders expect from Moriarti Armaments.

Features

Barrel

• Caliber: .300 AAC Blackout
• Length: 10.5"
• Heavy Profile
• 41V50 Steel
• Nitride Finish
• Twist Rate: 1:7
• Thread Pitch: 5/8x24
• Pistol-Length Gas System
• .750" Gas Block Journal

Upper Assembly

• Forged 7075-T6 Flat Top Upper Receiver
• Hard Coat Anodized
• M4 Feed Ramps
• Forward Assist Installed
• Dust Cover Installed
• A2 Flash Hider
• Crush Washer Included

Handguard

• 10" Slim Free Float M-LOK Rail
• Aircraft-Grade Aluminum
• Hard Coat Anodized
• Lightweight Design

Lower Build Kit

• Complete Mil-Spec Lower Parts Kit
• Mil-Spec Charging Handle
• SBA3 Adjustable Brace
• Mil-Spec Buffer Tube Assembly

Kit Includes

• Complete Upper Assembly
• 10.5" .300 Blackout Barrel
• Free-Float M-LOK Handguard
• Complete Lower Parts Kit
• SBA3 Adjustable Brace
• Buffer Tube Assembly
• Charging Handle

Does NOT Include

• 80% Stripped Lower Receiver

Why Choose a 10.5" .300 Blackout?

The 10.5-inch barrel remains one of the most popular lengths for .300 Blackout because it balances compact handling with reliable performance. Combined with the pistol-length gas system and threaded muzzle, it's an excellent platform for shooters building a compact AR-15.

Made in USA

All major components are manufactured in the USA using Mil-Spec standards for durability, compatibility, and dependable performance.

Important Information

• Ships unassembled.
• Compatible with most Mil-Spec AR-15 lower receivers.
• This builder kit is not an FFL item because the lower receiver is not included.
• Product images may vary slightly from the final configuration.