In 1948, while drawing on lessons learned from German and Russian advances in small arms technology, the Brits started from scratch. They wanted a weapon that was lethal out to normal infantry ranges, easy to manipulate, offered increased hit potential and was capable of full-auto fire. It was immediately apparent that the .303 cartridge was out. Its rimmed design made feeding from high-cap mags problematic, it was overly powerful and the weight of the round limited the number that could be carried. And for the sake of commonality, the Brits wanted a round compatible with every light support weapon or medium machine gun. As such, in order to comply with British doctrine, the bullet had to be effective out to 800 meters.
Out came a 7mm solution. The resulting .280 British round launched a 140-grain bullet at 2,500 fps and offered better long-range terminal ballistics with less recoil, weight and muzzle blast and with increased accuracy.