Davidson Defense Halcyon 10.5-inch Pistol-Gas 1:8 .300 BLK AR-15 Freefloat M-Lok Handguard Pistol Upper Build Kit

Halcyon 10.5-inch Pistol-Gas 1:8 .300 BLK AR-15 Freefloat M-LOK Pistol Upper Build Kit

The Halcyon is a .300 Blackout AR-15 Upper Build Kit built around a compact 10.5-inch pistol-length gas platform. The kit centers on a 10.5-inch HBAR profile parkerized barrel with a 1:8 twist rate and 5/8x24 thread pitch, paired with a Steel Flash Can Design 4 in black oxide and a black 5/8-inch crush washer. A micro low-profile steel gas block at 0.750 diameter and a pistol-length gas tube are included on the front end. The 7075-T6 aluminum anodized upper receiver features M4 feed ramps, a forward assist, and an ejection port door assembly, paired with a 12-inch MX10 freefloat M-LOK handguard. BCG and charging handle are not included.

Key Features

• 10.5-inch HBAR profile parkerized barrel, 1:8 twist, 5/8x24 thread pitch, .300 Blackout
• Pistol-length gas system
• Pistol-length gas tube
• Micro low-profile steel gas block, 0.750
• Steel Flash Can Design 4, black oxide finish, 5/8x24, black 5/8-inch crush washer included
• 7075-T6 aluminum upper receiver, anodized, M4 feed ramps, forward assist, ejection port door assembly
• 12-inch MX10 freefloat M-LOK handguard
• BCG and charging handle not included

Perfect For

• Builders sourcing a .300 Blackout AR-15 pistol upper build kit with a 10.5-inch HBAR parkerized barrel, 7075-T6 anodized upper receiver with forward assist, Steel Flash Can Design 4 at 5/8x24, and 12-inch MX10 freefloat M-LOK handguard, pairing it with their own bolt carrier group and charging handle
• Shooters building a compact 10.5-inch pistol-gas .300 Blackout platform who prefer to select their own BCG while having the HBAR parkerized barrel, anodized upper receiver with M4 feed ramps and forward assist, and MX10 freefloat M-LOK handguard covered in one kit
• AR-15 pistol builders who want a .300 Blackout upper build kit with a Steel Flash Can Design 4 at 5/8x24 and a 12-inch MX10 freefloat M-LOK handguard without sourcing components separately

Barrel and Muzzle Device

The 10.5-inch HBAR profile barrel is chambered in .300 Blackout with a parkerized finish, 1:8 twist rate, and 5/8x24 thread pitch, which matches the included Steel Flash Can Design 4 in black oxide. A black 5/8-inch crush washer, a micro low-profile steel gas block at 0.750 diameter, and a pistol-length gas tube cover the front end gas configuration on this pistol-length platform.

Upper Receiver and Handguard

The 7075-T6 aluminum upper receiver carries an anodized finish with M4 feed ramps, a forward assist, and an ejection port door assembly. The 12-inch MX10 freefloat M-LOK handguard features M-LOK attachment points along the body for accessory mounting. These two components define the exterior structure of the upper assembly on this AR-15 pistol platform.

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