Slightly off topic, but here's an interesting reference to tumbling birdshot rather than roundballs from late 18th century. In Wm. Cleator's book An Essay on Shooting, 1789, he mentions "patent milled shot", and then in a footnote explains:
Spencer
The patent milled shot is said to be made in the following manner. Sheets of lead, whose thickness corresponds with the size of the shot required, are cut into square stripes by a machine, and thus again into small pieces that are cubes, or of the form of a die. A great quantity of these little cubes are put into a large hollow iron cylinder, which is mounted horizontally and turned by a winch; when by their friction against one another and against the sides of the cylinder, they are rendered perfectly round and very smooth. The other patent shot is cast in moulds in the same way as bullets are.
Spencer