Product Review: The HK416 and the MR556A1

Heckler and Koch (HK) is a German firm known for supplying military and police forces with some of the best firearms currently available. HK rifles have traditionally worked with a system of bolt rollers that lock the action shut, but the company has become more mainstream with its G36 assault rifle, which uses a gas piston system. HK has also applied its considerable experience to troubleshoot and improve the British SA-80 bullpup rifle.

So, what happens when HK takes its considerable design expertise and applies it to America’s standard battle carbine, the M4?

The HK416, HK’s product-improved M4, replaces the conventional AR’s gas tube with a solid push rod, helping keep carbon and firing residue out of the upper receiver. The HK416 was originally produced at the request of US special operations troops who wanted a reliable, low-maintenance rifle that would function in all environmental conditions and with or without a sound suppressor.

While the HK416 got its start as a Special Forces rifle, current issuance and usage in the U.S. Special Operations community appears to be limited. Rumors abound about premature parts wear, breakage, and the rifle being too expensive with too many unique spare parts, making field repair difficult.

However, the HK416 has found success as the USMC’s new Infantry Automatic Rifle and is being used by various military and police departments across the globe, with Norway being a notable user.

The civilian version of the HK416 is dubbed the MR556A1. It is chambered for 223 Remington and 5.56 NATO cartridges but lacks the chrome-plated chamber and bore of its military counterpart. HK believes that best accuracy comes with an unlined bore, as chrome-lining can sometimes mask imperfections and negatively affect accuracy.

The MR556A1 features a 16.5″ barrel with a 1×7 twist, free-floated and covered by a removable quad rail housing the gas piston and push rod. The rifle uses a crisp, clean two-stage trigger, albeit a bit heavy at around seven pounds.

The MR556A1 has the potential to be far more reliable than a standard AR-15. HK engineers redesigned the bolt, eliminating gas rings and creating a longer, more substantial bolt. The gas piston parts are heavy and beefy, requiring an increased height of the top rail to house them.

Other improvements include a captured firing pin retainer, a firing pin block that locks the firing pin until the trigger is pulled, and a safety lever that can be rotated to safe with the hammer in the forward position.

On the range, the MR556A1 performed flawlessly with various magazines and ammunition. The unique shape of the magazine well may cause fitment issues with some plastic magazines, but USGI aluminum, HK steel, and Surefire’s 60-round quad stack magazines worked fine.

The unlined barrel lived up to HK’s accuracy claims, shooting as well as expected from a rifle of this quality. The MR556A1 upper receiver proved compatible with other AR-15 lower receivers, although internal parts may differ from other piston ARs.

The MR556A1 has two main drawbacks: weight and price. The rifle’s quad rail handguard and heavy profile barrel result in an empty weight of over eight pounds, putting it in the same class as some AR-10 308 rifles. Additionally, the MR556A1 is substantially more expensive than piston-driven ARs from competing manufacturers.

Conclusion

Despite its weight and price, the MR556A1 boasts an impressive design pedigree and delivers flawless performance. Its improvements over the standard AR-15, such as the redesigned bolt and carrier, firing pin block, and safety lever modification, contribute to increased reliability and functionality.

While it may not be the most cost-effective option, the MR556A1 is a well-engineered and reliable piston-driven AR-15 that showcases HK’s expertise in firearms design and development.

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