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

Spartacus 16-inch .300 Blackout AR-15 Complete Upper

The Spartacus is built around a Davidson Defense 16-inch .300 Blackout HBAR barrel, finished in phosphate, paired with a 7075-T6 aluminum upper receiver finished in black anodizing. It pairs a 15-inch black chrome ultra-lightweight M-LOK free-float handguard with an AR-15/AR-10 GI birdcage flash hider at the muzzle, running on a pistol-length gas system. A complete bolt carrier group and Mil-Spec charging handle round out the upper, giving the buyer everything needed on the upper side.

Key Features

• Davidson Defense 16-inch .300 Blackout HBAR barrel, 1:8 twist, phosphate finish
• Pistol-length gas system with micro low-profile steel gas block
• 7075-T6 aluminum upper receiver, black anodized finish
• 15-inch black chrome ultra-lightweight M-LOK free-float handguard, monolithic top rail
• AR-15/AR-10 GI birdcage flash hider, compatible with .308, 7.62x39, and .300 Blackout
• Complete bolt carrier group and Mil-Spec charging handle included

Barrel and Gas System

The Davidson Defense barrel runs 16 inches long, chambered in .300 Blackout and finished in phosphate with an HBAR profile. It carries a 1:8 twist rate and a 5/8x24 muzzle thread. Gas cycles back to the action through a pistol-length system, running a pistol-length gas tube and a micro low-profile steel gas block sized to a .750-inch diameter.

Upper Receiver and Handguard

The upper receiver is machined from 7075-T6 aluminum and finished in black anodizing, cut with M4 feed ramps for smooth feeding and fitted with an AR-15 forward assist assembly. The ejection port carries a standard .223/5.56 door with its rod and spring installed. Over the barrel sits a 15-inch handguard finished in black chrome, free-floated and using an M-LOK attachment system with a monolithic top rail running along its length.

Muzzle Device

Capping the muzzle is an AR-15/AR-10 GI birdcage flash hider, listed as compatible with .308, 7.62x39, and .300 Blackout. It threads onto the barrel's 5/8x24 pattern and is secured with the included 5/8-inch black crush washer.

Bolt Carrier Group and Charging Handle

A complete AR-15 bolt carrier group is included, made in the USA and listed for use across 5.56 NATO, .223 Remington, .300 Blackout, and .350 Legend. That broader listing describes the BCG itself; the barrel and chambering on this upper remain .300 Blackout. A Mil-Spec AR-15 M4 charging handle rounds out the upper's operating components.

Follow all manufacturer instructions and safe handling practices.

Ensure compliance with all applicable federal, state, and local laws.