TacFire BU-556-10 Pistol Upper Assembly 5.56x45mm NATO Caliber with 10" Black Nitride Barrel, Black Anodized 7075-T6 Aluminum Receiver & M-LOK Handguard for AR-Platform Includes Bolt Carrier Group

The TacFire BU-556-10 is a complete AR-platform pistol upper assembly in 5.56x45mm NATO, designed for shooters building a short-barreled AR pistol or upgrading an existing lower receiver. This is a fully assembled upper—barrel, bolt carrier group, and receiver all pre-installed—so if you've got a lower and lower parts kit on hand, you're ready to start shooting. No gunsmithing required.

Built on a 7075-T6 aluminum receiver with hard-coat black anodizing, the BU-556-10 is designed to take the wear of regular use. The 10-inch barrel is finished in black nitride, a corrosion-resistant treatment that handles both range sessions and field conditions. The handguard uses M-LOK slots, giving you modern mounting options for lights, grips, and other rail-mounted gear without committing to a full Picatinny rail system.

Since the bolt carrier group comes already installed, you're not hunting for compatible parts or worrying about headspace—the unit ships ready to function once mated to a compatible lower. This makes the BU-556-10 a straightforward choice for AR pistol builders who want a no-fuss upper assembly and don't want to source and assemble individual components.

Key Features

• Complete 5.56x45mm NATO pistol upper assembly—no additional parts needed to function
• 10-inch black nitride barrel for short-range and defensive use
• 7075-T6 aluminum receiver with hard-coat black anodizing for durability
• M-LOK handguard for flexible accessory mounting
• Bolt carrier group included and pre-installed
• AR-platform compatible—works with standard lower receivers

Specifications

Frequently Asked Questions

Will this upper work on my existing AR lower receiver?

Yes, the BU-556-10 is compatible with standard AR-platform lower receivers. You'll need a lower and lower parts kit to complete the rifle; the upper assembly itself includes everything else.

Does this come with a bolt carrier group?

Yes, the bolt carrier group is included and pre-installed in the upper assembly, ready to function as soon as it's mated to a compatible lower.

What's the advantage of a 10-inch barrel on an AR pistol?

A 10-inch barrel makes for a compact, maneuverable platform suitable for close-quarters shooting, home defense, and vehicle use. It keeps velocity adequate for 5.56x45mm while minimizing overall length—important if you're building an SBR or pistol configuration.

Can I add optics and accessories to the M-LOK handguard?

The M-LOK slots allow you to attach compatible optics mounts, lights, foregrips, and other tactical accessories. You'll need M-LOK-compatible mounting hardware for each item.