HK MR556 A4 Pistol

The MR556 is Heckler & Koch's commercial version of the HK416, and this is the pistol configuration with an 11-inch barrel. The A4 series is HK's latest update to the commercial HK416 and HK417 line, adding fully ambidextrous controls, lighter weight, a slimmer profile and an adjustable gas regulator.

It's chambered in 5.56x45mm and uses HK's short-stroke gas piston with an adjustable gas regulator. On a short barrel, that regulator is especially useful, since it helps tune the gas for the shorter dwell time and for use with a suppressor.

The barrel has six lands and grooves with a 1-in-7-inch twist, which stabilizes a wide range of bullet weights, and the muzzle is threaded 1/2x28. The pistol measures 31.7 inches long and weighs 6.7 pounds without a magazine, a handy size for a piston-driven 5.56mm.

The controls are fully ambidextrous, and the A4 is lighter and slimmer than earlier models, which makes the pistol easier to handle and carry. An M-LOK free-float handguard gives you room for lights and grips. HK includes one magazine, in 30 or 10-round capacity depending on the model.

If you want a compact 5.56mm with real HK engineering and the piston system of the HK416, the MR556 A4 Pistol is a well-built option. It's a practical size for close work and a natural base for a suppressor. Check your state and local rules on pistols and braces before you buy.