White Label Davidson Defense 'Esper Sentinel' 10.5-inch AR-15 .300BLK Phosphate Pistol Upper Build Kit

Davidson Defense Esper Sentinel 10.5-inch AR-15 .300BLK Phosphate Pistol Upper Build Kit

This is a complete AR-15 .300BLK pistol upper built on a 7075-T6 aluminum receiver with a 10.5-inch 4150 CrMoV phosphate barrel and 9-inch M-Lok handguard. The upper includes a pistol length gas tube, micro low-profile gas block, forward assist assembly, ejection port door with rod and spring, muzzle device, and crush washer. BCG and charging handle are not included.

Key Features

• 10.5-inch HBAR barrel with 1:8 twist rate in .300 Blackout
• 7075-T6 aluminum upper receiver with anodized finish
• 9-inch M-Lok handguard for accessory mounting
• Pistol length gas system with micro low-profile gas block
• 5/8x24 threaded muzzle with GI birdcage flash hider included
• M4 feed ramps for reliable feeding
• Forward assist assembly and ejection port door included

Perfect For

• Pistol builds using .300BLK for subsonic ammunition
• Shooters wanting a compact upper with proven barrel profile
• Builds prioritizing short sight radius and maneuverability
• Those building on existing AR-15 lower receivers

Compact Pistol Caliber Platform

The .300BLK caliber excels with shorter barrel lengths like this 10.5-inch configuration. The 1:8 twist rate stabilizes both subsonic and supersonic loads effectively. This upper pairs naturally with pistol length gas systems, creating a balanced short-range platform that cycles reliably across ammunition types. The HBAR profile provides consistent accuracy without excessive weight for a pistol configuration.

M-Lok Accessory Ecosystem

The 9-inch M-Lok handguard integrates with the modern modular mounting standard. Accessory rails attach directly to the handguard slots, eliminating the need for rail segments or adapters. This design keeps the upper streamlined while maintaining full customization capability for optics, lights, and other tactical attachments.

Phosphate Barrel Durability

The 4150 CrMoV barrel with phosphate finish delivers corrosion resistance and proven reliability. Phosphate coating bonds directly to the steel surface, providing protection without adding significant weight. This finish standard has been used in military applications for decades and handles both suppressed and unsuppressed fire equally well.

Complete Upper Assembly Ready

This upper arrives with all primary components assembled and tested. The forward assist, ejection port door, gas block, and gas tube are installed. The included muzzle device threads directly onto the barrel. Simply attach to your lower receiver and add a bolt carrier group and charging handle to complete the rifle.

Follow safe handling and manufacturer instructions. Ensure compliance with all applicable federal, state, and local laws. BCG and charging handle are not included.