The adoption of the 7.62×51mm NATO round and the adaptation of the intermediate cartridge CETME (later developed into the G3) and FN FAL designs to fire it, produced rifles that were relatively longer and heavier and had greater recoil.
While designing the CETME Modelo B and under recommendation of H&K, the decision was made that the updated version of the original CETME Modelo A would chamber the more powerful 7.62×51 NATO cartridge.