Heckler & Koch · Rifle
Heckler & Koch MR556 A4
Gas operated short stroke · 5.56x45mm NATO · introduced 2025
Also known as MR556A4
About the Heckler & Koch MR556 A4
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.
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.
Heckler & Koch MR556 A4 specifications
General
- Type
- Rifle
- Action
- Gas operated short stroke
- Firing mechanism
- Rotating bolt
- Trigger
- Single stage
- Trigger pull
- 2.2 kg (4.9 lb)
- Calibres
- 5.56x45mm NATO
- Magazine capacity
- 30 rounds
- Magazine
- Detachable box magazine
Dimensions
- Barrel length
- 419 mm (16.5 in)
- Overall length
- 927 mm (36.5 in)
- Height
- 191 mm (7.5 in)
- Width
- 78 mm (3.1 in)
- Weight (empty)
- 3.48 kg (7.67 lb)
Barrel
- Rifling twist
- 1:7 in (178 mm)
- Rifling
- Right hand
Materials
- Barrel
- Steel
- Receiver / frame
- Aluminum
- Stock
- Polymer
- Finish
- Black
Performance
- Muzzle velocity (typical)
- 900 m/s (2953 fps)
- Effective range
- 500 m
History
- Introduced
- 2025
- Production status
- In production
- Country of origin
- DE
Features
- Short stroke gas piston
- Adjustable gas regulator
- Cold hammer forged barrel
- Ambidextrous controls
- M lok handguard
- Collapsible stock
- Lifetime barrel warranty
Safety
- Ambidextrous safety selector
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.
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