Optimized for suppressed and CQB applications, the 11-inch MR556 A4 upper is built around HK’s short-stroke gas piston system with an adjustable gas block, enabling smooth function with or without a suppressor. The 1/2x28 threaded barrel is concentric and precision-machined, ensuring compatibility with muzzle devices and suppressors.
It includes a monolithic M-LOK handguard with integrated ambidextrous QD sling cups, a continuous Picatinny rail for optics and sights, and an ambidextrous charging handle with dual claw extensions. The match-grade cold hammer-forged barrel provides outstanding accuracy and barrel life, while the included bolt carrier group, charging handle, buffer weight, and buffer spring make this upper fully operational out of the box.
- Manufacturer: Heckler & Koch (HK)
- Model: MR556 A4 Upper Receiver
- Series: MR556
- Category: Uppers
- Caliber: .223 Remington / 5.56 NATO
- Barrel Length: 11"
- Thread Pattern: 1/2x28
- Firearm Fit: AR-15 Lower Receivers
- Handguard: M-LOK Interface with Integral Ambi QD Cups
- Rail: Continuous Picatinny (Upper to Handguard)
- Charging Handle: Extended Ambidextrous with Dual Claws
- Barrel Type: Match-Grade Cold Hammer-Forged
- Gas System: Adjustable Regulator (Suppressed/Unsuppressed)
- Finish: Anodized
- Color: Black
- Includes: Bolt Carrier Group, Charging Handle, Buffer Weight, Buffer Spring
