HK MR556 A4 Complete Upper Receiver - 11" Match Grade Barrel

HK MR556 A4 Complete Upper Receiver - 11" Match Grade Barrel

The Heckler & Koch MR556 A4 Upper Receiver Kit is the ultimate upgrade for serious shooters seeking unmatched reliability, precision, and suppressor-ready versatility. Built on the legendary HK416 platform and assembled in the USA with premium German and American components, this upper transforms any Mil-Spec AR-15 lower into a battle-proven piston-driven system trusted by elite military and law enforcement units worldwide.

Featuring a cold hammer-forged match barrel, adjustable gas regulator, and extended ambidextrous charging handle, the MR556 A4 delivers flawless performance whether you're running suppressed or unsuppressed. The closed piston system eliminates carbon fouling in the receiver, drastically reducing maintenance and increasing operational reliability under harsh conditions.

With a sleek anodized black finish, M-LOK handguard, and continuous Picatinny rail, this upper is ready for any mission. Whether you're upgrading your duty rifle or building a premium tactical setup, the MR556 A4 is engineered to dominate.

Suppressor-Ready Barrel
Concentric 1/2x28 threads ensure perfect alignment for suppressor use.

Adjustable Gas Regulator
Easily switch between suppressed and unsuppressed configurations for optimal performance.

Cold Hammer-Forged Barrel
Match-grade 11" barrel delivers exceptional accuracy and durability.

Piston-Driven System
Replaces traditional gas tube with piston and pusher rod for cleaner, more reliable operation.

M-LOK Handguard
Lightweight and modular with integral ambidextrous QD sling cups for enhanced versatility.

Extended Ambidextrous Charging Handle
Dual claw design for fast, intuitive manipulation from either side.

Continuous Picatinny Rail
Seamless top rail between receiver and handguard for maximum optics flexibility.

Complete Kit
Includes bolt carrier group, charging handle, buffer weight, and buffer spring for full compatibility.

Specifications

• Caliber: .223 Remington / 5.56 NATO
• Barrel Length: 11"
• Barrel Type: Cold hammer-forged, match-grade
• Threading: 1/2x28, suppressor-ready
• Gas System: Adjustable piston with pusher rod
• Handguard: M-LOK interface with integral ambidextrous QD sling cups
• Rail System: Continuous Picatinny between upper and handguard
• Charging Handle: Extended ambidextrous with dual claws
• Finish: Anodized black
• Compatibility: Fits Mil-Spec AR-15 lower receivers
• Included Components: Bolt carrier group, charging handle, buffer weight, buffer spring