It has always been my understanding that "chilled" shot is slightly harder than "dropped"shot, the difference in the names of each being slightly erroneous as both were formed by being dropped. I think there was a difference in the way the shot was cooled, how quickly, etc., that gave the chilled shot a very slightly greater hardness, having nothing to do with the addition of antimony.
I do know that there is a procedure whereby one may temper soft lead shot to increase the hardness, by using an oven and a quench. PA 24 wrote me once and described the process in great detail.
SRH
