The Heckler & Koch HK417 is a battle rifle designed and manufactured in Germany by Heckler & Koch. It is a gas-operated, selective fire rifle with a rotating bolt and is essentially an enlarged HK416 assault rifle. Chambered for the full power 7.62x51mm NATO round, instead of a less powerful intermediate cartridge, the HK417 is intended for use as a designated marksman rifle, and in other roles where the greater penetrative power and range of the 7.62x51mm NATO round are required. It has been adopted for service by a number of armed forces, special forces, and police organizations.
The HK417 is similar in internal design to the HK416, but the receiver and working parts are enlarged to suit the larger 7.62x51mm NATO round. The bolt is a 7-lug rotating type, which sits in a bolt carrier and operates in a forged alloy receiver resembling those of the Stoner-designed AR-10, AR-15 and M16 series weapons. Like the HK416, the HK417 is a gas-operated, with a short-stroke piston design similar to those found G36. The short-stroke piston is more reliable than the original direct impingement operation of the AR-10 and AR-15 designs because, unlike these weapons, it does not vent propellant gases directly into the receiver, which deposits carbon fouling onto the bolt mechanism as well as heating it up; such carbon fouling leads to more malfunctions.