 The HK417 is similar in internal design to the HK416, although the receiver and working parts are enlarged to suit the larger 7.62×51mm cartridge.The bolt is a seven-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 rifles.Like the HK416, the HK417 is gas-operated with a short-stroke piston design similar to that of the Heckler & Koch G36.