Davidson Defense Three Hundo 16-Inch AR-15 .300 BLK Rifle - Full Build Kit

Three Hundo 16-Inch AR-15 .300 BLK Rifle - Full Build Kit

The. Three. Hundo is a complete. Davidson. Defense full build kit chambered in .300 Blackout. This configuration pairs a 16-inch 4150 Chrome. Moly barrel with a free float quad rail handguard, delivering a compact platform optimized for subsonic ammunition and suppressed shooting. The kit includes everything except the lower receiver, making it ready for final assembly by the end user.

Key Features

• 16-inch 4150 Chrome Moly Vanadium barrel with 1:8 twist rate, optimized for .300 BLK subsonic loads
• Free float 15-inch quad rail handguard for accessory mounting and improved accuracy
• Pistol-length gas system with 0.75-inch gas block for reliable cycling
• 8620 alloy steel bolt carrier with nitride finish for durability
• Gauntlet Arms Special Operations stock in glass-filled polymer
• Mil-spec charging handle and carbine buffer tube compatibility
• GI Birdcage flash hider with 1/2x28 thread pitch

Perfect For

• Shooters building a .300 Blackout platform for subsonic suppressed shooting
• Hunters seeking a compact rifle with reduced noise signature
• Builders who want a complete upper and lower component set without the serialized receiver
• Users prioritizing modularity and accessory mounting flexibility

Three Hundo Platform Overview

The. Three. Hundo delivers .300 Blackout performance in a compact 16-inch configuration. The 1:8 twist rate stabilizes subsonic projectiles reliably, and the pistol-length gas system keeps the action smooth while minimizing felt recoil. The free float quad rail separates the handguard from the barrel, eliminating harmonic interference and supporting consistent accuracy. This design prioritizes suppressed fire and close-quarters effectiveness over long-range precision.

Barrel and Gas System Design

The 4150 Chrome. Moly. Vanadium barrel provides durability for repeated shooting cycles and ammunition variations. Phosphate finish protects against corrosion while maintaining a traditional appearance. The HBAR profile balances weight and stiffness, and the 5/8x24 muzzle thread accepts standard .300 BLK suppressors. Pistol-length gas system operation cycles reliably with both supersonic and subsonic ammunition, a key advantage for this caliber platform.

Upper Assembly and Handguard Configuration

The 7075-T6 aluminum upper receiver is anodized for corrosion resistance and durability. The 15-inch free float quad rail handguard provides four picatinny rail surfaces for mounting optics, lights, lasers, and other tactical accessories. Aircraft-grade aluminum construction keeps weight minimal while maintaining rigidity. Free float design means the handguard never touches the barrel, eliminating vibration that could affect shot placement.

Lower Component Set and Stock

This full build kit includes the bolt carrier group, charging handle, buffer tube, buffer, recoil spring, end plate, castle nut, and lower parts kit. The. Gauntlet. Arms. Special. Operations stock offers a comfortable cheek weld and adjustable length of pull across six positions. Glass-filled polymer construction resists impact while keeping overall weight manageable. Mil-spec compatibility ensures the buffer tube fits standard AR-15 lower receivers.

Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws. Lower receiver not included. BCG and charging handle are not included with upper build kits only, but this full build kit includes both.