More modern shot towers were used, at least until lead shot was banned for bird hunting in the US. It's actually one of the most efficient ways of making "little round things" in very large quantities, and it supposedly is surprisingly simple to select a specific "drop" size and make the shot very consistently nearly all of the same selected size.
Newer ones of course had all kinds of "isolation areas" and air filters and fume traps and the like to reduce the rate at which the operators had to be replaced.
The tower had to be tall enough for the lead bits to harden before hitting a pool of water at the bottom, so that the impact with the water wouldn't flatten them. A liquid drop falling through air can be something rather non-spherical, so some towers had features that attempted to make the air flow inside the tower approximately match the drop velocity, at least down to where the shot "firmed up some."
The falling shot itself will entrain enough air to set up an approximately ideal air flow if the top of the tower is "leaky enough," but if done by accident as in the older towers that can (especially with lead) just spread the contamination around the whole neighborhood. Without some air flow, the air heats up and it takes longer for the balls to harden (and either a taller tower is needed, or "shorter runs" must be made).
A similar method, with much more complex machinery of course, has been used to make small steel balls for ball bearings, although I don't believe anyone is still doing it with towers in that trade.