Geissele Automatics Mk16 11.5'' Urgi Upper Chf Barrel Ach Rebcg 5.56Mm Ddc

The Geissele Automatics Mk16 11.5" URGI upper receiver is a combat-proven, complete upper assembly built on the design that's currently in service with U.S. Army Special Operations Command. This 5.56 NATO upper pairs a hammer-forged, chrome-lined barrel with Geissele's modular rail system and reliability-enhanced bolt carrier group—a no-compromise setup for shooters who demand precision, durability, and real-world performance in a compact footprint.

The 11.5" barrel runs a carbine-length gas system with government profile, 1/7 twist, and chrome moly construction rated for the demands of modern 5.56 ammunition. Everything is pinned where it matters: the low-profile gas block is secured tight, and the SureFire 4-prong flash hider is welded in place. You get Geissele's Reliability Enhanced Bolt Carrier Group, Airborne Charging Handle in DDC (Desert Dirt Color), and a Super 42 braided buffer spring paired with an H3 buffer, tuned for the carbine-length gas tube on this configuration. The Geissele Super Modular Rail MK16 handguard rides on top, purpose-built for shootability and modularity.

This is an upper you install on an existing lower to build a complete rifle. Whether you're assembling a precision 3-gun rifle, a duty rifle, or a compact precision platform, the Mk16 11.5" URGI delivers the ergonomics and predictable performance that come from tested-in-theater engineering.

Key Features

• Complete upper assembly — barrel, handguard, bolt carrier group, charging handle, and gas block included and assembled
• Hammer-forged, chrome-lined 11.5" barrel with carbine-length gas system, 1/7 twist
• Geissele Super Modular Rail MK16 for modularity and low-profile mounting
• Geissele Reliability Enhanced Bolt Carrier Group for smooth operation and proven reliability
• Low-profile gas block, pinned in place for permanent zero
• SureFire 4-prong flash hider, pinned and welded
• Geissele Airborne Charging Handle in DDC
• Super 42 braided buffer spring and H3 buffer included
• Government profile, chrome moly construction rated for M855A1 duty ammunition

Specifications

Frequently Asked Questions

What lower receiver is this upper compatible with?

This is a Mil-Spec M4 upper receiver assembly. It will fit any standard AR-15 lower receiver with a Mil-Spec receiver extension.

Can I swap the handguard or gas block?

The Geissele Super Modular Rail MK16 uses standard MIL-STD-1913 Picatinny mounting, so optics and accessories are fully compatible. The gas block is pinned in place, which is a permanent installation for zero integrity.

What ammunition is this barrel designed for?

The barrel is hammer-forged and chrome-lined with chrome moly construction, rated for the full spectrum of 5.56 NATO duty ammunition, including modern variants like M855A1. It is not a .223 Remington-only barrel.

Is this a complete rifle or just an upper?

This is a complete upper receiver assembly. You will need to pair it with an AR-15 lower receiver to have a functional rifle.