Description
Heckler & Koch MR556 A4 upper receiver kit is a complete upper receiver and barrel assembly for .223 Remington/5.56 NATO retrofits using the HK piston and pusher rod system. The barrel is 16.5 in, with a 1/2×28 thread pitch. The handguard is M-LOK compatible, and the kit is supplied with key upper components for assembly.
Key features
- Complete upper receiver and barrel assembly
- Closed piston and pusher rod system replaces the gas tube method
- M-LOK handguard
- 1/2×28 threaded muzzle interface
Specifications
| Fits | AR-15 lower receivers |
|---|---|
| Part Type | Upper Receiver/Barrel Assembly Kit |
| Caliber | .223 Remington/5.56 NATO |
| Barrel Length | 16.5 in |
| Thread Pitch | 1/2×28 |
| Rate of Twist | 1-in-7" |
| Material | Stainless |
