HK MR556 A4 11" Upper

The HK MR556 A4 11" Upper is a complete upper receiver kit that converts a Mil-Spec AR-15 style lower to HK's piston and pusher rod operating system. Built around an 11-inch cold-hammer forged barrel chambered in 5.56 NATO, it brings the same closed gas system design that defines the MR556 rifle. It suits shooters who want HK reliability and a cleaner-running action on a short, maneuverable platform.

The kit ships complete with the MR556 bolt group, HK's tungsten-filled proprietary buffer and action spring, and an adjustable gas block for running with or without a suppressor. HK notes that the shortened buffer and action spring are not intended for fixed-stock AR/M16-type rifles, and non-HK lowers require a Mil-Spec hammer.

Features

• HK piston and pusher rod system in place of a standard gas tube
• Cold-hammer forged 11" barrel with 1:7 twist
• Threaded 1/2x28 muzzle
• Adjustable gas block for suppressed or unsuppressed use
• HK free-floating rail system handguard
• Extended convertible charging handle and forward assist
• Includes complete bolt group, tungsten-filled buffer, action spring and soft case

Specifications

• Manufacturer: Heckler & Koch (HK USA)
• Manufacturer Part #: 51000385
• UPC: 642230270220
• Type: Complete upper receiver kit
• Caliber: 5.56x45mm NATO
• Barrel Length: 11 in.
• Twist: 1:7 right hand, 6 lands and grooves
• Muzzle Thread: 1/2x28
• Operating System: Piston and pusher rod
• Handguard: HK Free Floating Rail System
• Kit Weight: 4.20 lb.
• Kit Length: 17 in.

In stock at Cajun Gun and Gear, 108 Youngsville Hwy, Lafayette, LA. Call 337.999.0373 to check availability or stop by to see it in person.