Heckler & Koch MR556 A4 Upper Receiver Features
This upper receiver kit includes everything you need for a top-tier build: a bolt carrier group, charging handle, buffer weight, and buffer spring. The 16.5-inch barrel features concentric 1/2×28 threads for suppressor compatibility, paired with an adjustable gas regulator to ensure reliable cycling whether suppressed or unsuppressed. The cold hammer-forged barrel is designed for exceptional longevity and match-grade accuracy.
The M-LOK handguard with integrated ambidextrous QD sling cups offers robust mounting flexibility. A continuous Picatinny rail bridges seamlessly across the upper and handguard, providing an ideal surface for optics and accessories. The extended ambidextrous charging handle with dual claws makes manipulation fast and intuitive, whether you’re running slick or gloved.
Heckler & Koch MR556 A4 Upper Receiver Specifications
- Manufacturer: Heckler & Koch (HK)
- Model: MR556 A4 Upper Receiver
- Series: MR556
- Category: Uppers
- Caliber: .223 Remington / 5.56 NATO
- Barrel Length: 16.5″
- Thread Pattern: 1/2×28
- Firearm Fit: AR-15 Lower Receivers
- Handguard: M-LOK Interface with Ambi QD Cups
- Rail: Continuous Picatinny (Upper to Handguard)
- Charging Handle: Extended Ambidextrous Dual-Claw
- Barrel Type: Match-Grade Cold Hammer-Forged
- Gas System: Adjustable Regulator for Suppressed/Unsuppressed
- Finish: Anodized
- Color: Black
- Includes: Bolt Carrier Group, Charging Handle, Buffer Weight, Buffer Spring
| Barrel Length | 16.5 |
|---|---|
| Caliber | 5.56 |
| Condition | New in Box |
| Finish Per Color | Black |
| Manufacturer | Heckler and Koch |
| Manufacturer Part Number | 51000384 |
| Model | MR556 A4 Upper Receiver |
| Type | Uppers |
| UPC | 642230270213 |
