Sling Stone Recreations. There were several different kinds of sling stones; smooth rounded rocks, clay, and lead. Before the Greeks, sling stones were larger, over 2 inches in diameter. The Greeks and Romans used smaller sling stones about the size of golf balls and smaller sling bullets, and they made them out of other materials like clay and lead. At the time of David, smooth stones over two inches were used in slings about the size of a tennis ball (I Samuel 17:40).