Heckler & Koch's HK416 (Mr223) test and disassembling

The Heckler & Koch 416 uses a proprietary gas system derived from the HK G36, replacing the direct impingement gas system used by the standard M16/M4. The HK system uses a short-stroke piston driving an operating rod to force the bolt carrier to the rear. This design prevents combustion gases from entering the weapons interior, a shortcoming with direct impingement systems