Heckler & Koch MR556 A4
Heckler & Koch · Rifle · In Production · 2025
Also known as: MR556A4
Overview
The Heckler & Koch MR556 A4 is the semi-automatic civilian counterpart to the HK416, chambered in 5.56x45mm NATO. It uses HK's short-stroke gas piston with an adjustable regulator for suppressed or unsuppressed fire, a cold-hammer-forged 16.5-inch barrel, fully ambidextrous controls and an M-LOK handguard, weighing about 7.67 pounds with a collapsible stock adjusting overall length between 33.25 and 36.5 inches.
Specifications
| Weight (empty) | 3479 g (122.7 oz) |
| Overall Length | 927 mm (36.50") |
| Barrel Length | 419 mm (16.50") |
| Height | 191 mm (7.52") |
| Width | 78 mm (3.07") |
| Action Type | Gas Operated Short Stroke |
| Firing Mechanism | Rotating Bolt |
| Trigger Type | Single Stage |
| Trigger Pull | 22 N (4.9 lbf) |
| Magazine Capacity | 30 rounds |
| Magazine Type | Detachable Box |
| Muzzle Velocity | 900 m/s (2953 fps) |
| Effective Range | 500 m (547 yd) |
| Barrel Rifling | Right Hand |
| Rifling Twist | 178 mm (7.01") |
| Frame Material | Aluminum |
| Barrel Material | Steel |
| Stock Material | Polymer |
| Finish | Black |
Calibers
- 5.56x45mm NATO · primary · 5.56x45mm NATO — also known as 5.56mm NATO, 5.56x45mm, .223 Remington
Features
- Firing modes: Semi Automatic
- Feed systems: Detachable Box Magazine
- Safety mechanisms: Ambidextrous Safety Selector
- Features: Short Stroke Gas Piston, Adjustable Gas Regulator, Cold Hammer Forged Barrel, Ambidextrous Controls, M Lok Handguard, Collapsible Stock, Lifetime Barrel Warranty
Variants
- Heckler & Koch MR556 A4 Pistol 11" — Pistol
Production
Production years: 2025-present
Origin
Country of origin: Germany
Notes
The A4 update brought fully ambidextrous controls, a lighter profile and HK's first lifetime barrel bore guarantee. An 11-inch pistol configuration is also offered. Added to close a catalogue gap - introduced in the 2025 model year.
Background
The HK416's piston system exists because Delta Force asked HK to fix the M4's gas-tube fouling in the early 2000s; the MR556 is the same engineering sold, semi-auto only, over a gun counter.