Following the revision of the OICWBlock 1 / XM8 program, the Heckler & Koch company decided to enter the US military and law enforcement markets with the alternative design, which, in fact, looks quite promising. Based on the experience, gained during successful upgrade program of the British SA80 / L85A1 program, HK decided to cure the existing M16 rifles and M4 carbines from most of their problems, inherent to this 40-years old design.The key improvements, made by HK, are their patented short-stroke gas piston system, borrowed from HK G36 rifle. This system replaced the direct gas system of standard M16 rifle, so no powder residue will remain in the receiver even after long shooting sessions. The “new"gas system also is self-regulating and will work reliably with any barrel length. Other improvements include new buffer assembly, improved bolt, and a cold hammer forged barrel, as well as free-floating hand guard with integral Picatinny-type rails. Originally developed as a "drop-in” upper receiver assembly for any standard M16/M4 type lower receiver, HK416 is also available as a complete weapon, with HK-made lower receivers. Current (late 2005) models include carbines with 10.5" and14.5" barrels, and 16.5" barrelled carbine and 20" barrelled rifle will be added later. 7
Another interesting development, which is apparently based on the up scaled HK416 design, is the HK417 - the 7.62x51 NATO rifle that combines AR-15/M16 type ergonomics, layout and handling with improved reliability of HK-made and designed gas piston system. This rifle probably will use HK G3-type magazines. If the rumours about HK417 are true, the 5.56mm HK416 / 7.62mm HK417 combination will be a direct rival to the newest FN SCAR system.
HK416 is a gas operated, selective fired weapon of modular design. It uses short-stroke gas piston that operates the 7-lug rotating bolt. Receiver is made from high grade aluminium alloy. Combination-type safety / fire selector allows for single shots and full automatic mode. Hk416 retains all M16-style controls, including last round bolt hold-open device, rear-based charging handle and magazine release button on the right side of the magazine well. HK416 is fitted with four Picatinny rails as standard, and may accept any type of sighting devices on STANAG-1913 compliant mounts. It also can accept modified HK AG36/AG-C 40mm grenade launcher, which is clamped directly to bottom rail. Butt-stock is of typical M4 design, multi-position telescoped.