Complex sentence: The next development was a special armour-piercing bullet, the K bullet (in German "Patrone SmK Kurz 7.92 mm"), which too could be fired from the regular infantry rifle.
Split into simpler sentences: The next development was a special armour-piercing bullet, the K bullet (in German "Patrone SmK Kurz 7.92 mm"). Again this could be fired from the regular infantry rifle.