Geissele Automatics Mk16 10.3'' Urgi Upper Chf Barrel Ach Rebcg 5.56Mm Ddc

The Geissele Automatics Mk16 10.3" URGI upper is a combat-proven complete upper receiver built to the exacting standard of U.S. Army Special Operations Command. This 5.56 NATO upper pairs a hammer-forged, chrome-lined barrel with Geissele's renowned components—a reliability-enhanced bolt carrier group, Super Modular Rail handguard, and precisely engineered gas system—to deliver a modular platform that transforms a lower receiver into a professional-grade short-barrel rifle. If you're building a compact duty gun, an SBR for CQB training, or a truck gun that doesn't sacrifice accuracy, the Mk16 10.3" brings field-tested engineering to your bench.

The 10.3" barrel runs a carbine-length gas system and 1/7 twist rate, tuned for 5.56 NATO and M855A1 duty rounds. Cold hammer-forged chrome-moly steel ensures durability under sustained fire, while the pinned SureFire SF4P flash hider keeps signature controlled. The Geissele Super Gas Block is already pinned in place—no guessing on gas block installation. Components are finished in Flat Dark Earth (DDC) for that cohesive, professional look. An H3 buffer comes ready to tune your spring/buffer tune out of the box.

This is not stripped or partial; it's a complete upper ready to bolt onto your lower receiver and run. No hidden fitment surprises, no assembly surprises. Geissele's reputation for controlled-round-count perfection carries through every part of this package. Whether you're an operator who knows the URGI platform or a serious builder seeking components trusted by SOF, the Mk16 10.3" upper delivers the kind of repeatability and reliability that justifies the investment.

Key Features

• Complete upper receiver assembly — bolt to your lower and shoot
• 10.3" hammer-forged, chrome-lined barrel with 1/7 twist and carbine gas system
• Geissele Reliability Enhanced Bolt Carrier Group for consistent lockup and extraction
• Geissele Super Modular Rail MK16 handguard for robust mounting and ergonomic control
• Geissele Airborne Charging Handle in Flat Dark Earth
• Pinned SureFire SF4P 4-prong flash hider for signature control
• Geissele Super Gas Block (low-profile, pinned for bombproof installation)
• Includes H3 buffer for carbine-length tuning
• Flat Dark Earth finish throughout for a clean, cohesive appearance

Specifications

Frequently Asked Questions

Is this a complete upper or do I need to buy parts separately?

This is a complete upper receiver assembly. Everything you see is included and assembled. You only need to attach it to a lower receiver to have a functioning rifle.

What lower receiver will this fit?

The Mk16 10.3" is a mil-spec M4 upper receiver assembly, so it will fit any mil-spec AR-15 lower receiver. Confirm your lower is mil-spec if you're unsure.

Why the 10.3" barrel length, and what's it good for?

The 10.3" barrel with carbine-length gas system is optimized for compact, maneuverable builds—ideal for short-range work, CQB training, vehicle setups, or SBR builds. It's still accurate within typical combat ranges while keeping overall length and weight minimal.

Does this come with a buffer?

Yes, an H3 buffer is included. This pairs with the carbine-length gas system for balanced cycling.