The first attempt at boosting penetrating power was the so-called 'reversed bullet'. This used the same cartridge and bullet as the regular round, but the bullet was "reversed" and an increased propelling charge was used. The next development was a special armour-piercing bullet, the K bullet (in German "Patrone SmK Kurz 7.92 mm"), which could also be fired from the regular infantry rifle. It had an increased propelling charge and a steel core bullet. This had about a 30% chance of penetrating the 8 mm armour of contemporary tanks if it struck the armour at a perpendicular angle.