Davidson Defense Spartacus 300BLK 16-inch Pistol-Gas 1:8 .300 Blackout AR-15 Freefloat M-Lok Handguard Rifle Upper Build Kit

Spartacus 300BLK 16-inch Pistol-Gas Upper Build Kit

This upper build kit delivers a complete 300 Blackout platform built around a 16-inch 4150 CrMoV barrel with a 1:8 twist rate designed for subsonic and supersonic ammunition. The pistol-gas system pairs with a micro low-profile gas block for reliable cycling without the weight of a full-size setup. A 15-inch freefloat M-Lok handguard provides mounting flexibility and accessory options while maintaining accuracy through barrel independence. The upper receiver uses 7075-T6 aluminum with M4 feed ramps for reliable feeding, and the barrel threads accept standard 5/8x24 muzzle devices for suppressor compatibility.

Key Features

• 16-inch 4150 CrMoV barrel with 1:8 twist optimized for 300 Blackout subsonic and supersonic loads
• Pistol-length gas system with micro low-profile gas block for compact operation
• 15-inch freefloat M-Lok handguard provides accessory mounting without barrel contact
• 7075-T6 upper receiver with M4 feed ramps and anodized finish
• 5/8x24 threaded muzzle brake ready for suppressor installation
• Includes forward assist assembly and ejection port door with spring

Perfect For

• Suppressed 300 Blackout builds using subsonic ammunition
• Shooters building compact pistol-gas AR-15 platforms
• Users seeking freefloat accuracy with tactical accessory mounting
• Builders pairing this upper with AR-15 lower receivers or pistol braces

Design and Platform Compatibility

This upper is purpose-built for the AR-15 platform and accepts standard mil-spec lower receivers. The 300 Blackout cartridge operates reliably with both subsonic loads for suppressed shooting and supersonic ammunition for extended range. The 1:8 twist rate stabilizes the wider range of bullet weights available in 300 Blackout, from lightweight 110-grain rounds to heavy 220-grain subsonic projectiles. The pistol-gas system reduces felt recoil compared to carbine-length systems while maintaining the compact profile needed for shorter platforms.

Freefloat Handguard and Accessory Ecosystem

The 15-inch freefloat design isolates the barrel from the handguard, eliminating contact that can affect accuracy. M-Lok slots along the handguard allow direct mounting of lights, lasers, grips, and rail segments without the need for additional adapters. The aluminum construction balances weight and durability for extended use. Freefloat designs are particularly valuable for precision shooting and consistent zero maintenance across different shooting positions.

Suppressor Ready Configuration

The 5/8x24 threaded barrel accepts standard suppressors and muzzle devices designed for this thread pitch. The included GI birdcage flash hider provides a baseline muzzle solution while you select a suppressor that matches your shooting needs. Subsonic 300 Blackout ammunition benefits significantly from suppression, allowing you to shoot hearing-safe loads without excessive muzzle blast.

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