7.62 X 37 H & K

This was developed at Radway Green at the request of Heckler & Koch, who were developing a rifle for silenced combat. They had previously studied the .300 Whisper cartridge but decided to develop their own as well, by shortening and necking-up the 5.56×45 case. The cartridge fires a Lapua B416 bullet weighing 13g (200 grain) at a muzzle velocity of 310 m/s. (1,017 fps)