In the early days of self-contained rifle cartridges, velocity was restricted by the use of blackpowder. So, to increase power, the bullets were made bigger and heavier.
Then, in the late 1800s, along came smokeless powder. It was discovered that smaller bullets could be used, and to increase power, velocity could be increased. The lead bullets didn’t do well with the higher velocity because they were too soft to hold the rifling. That led to jacketed bullets; a lead core, wrapped with a guiding metal jacket. These would expand on impact and create a larger frontal area, often matching the diameter of the
