Some time S-Ball was only one slug offered in Czechoslovakia. Primary it was designed for battue game. Plastic sabot allowed firing it form fully choked bores. Sellier Bellot stopped the production of S-Ball plastik more than 10 years ago because of prohibition steel core bullets. Probably it was few years produced with brass core too but original S Balls is steel.. 16 bore bullet weight 18 grams and 12 bore 24,6 grams. Length of cartridge was only one 65 mm it fit 70 mm chambers too.
I am surprised that it was used for buffalo shooting.
In Czech Republic are rumors that sometimes S-Balls ricochet from wild boars shoulder.
But I have no personal experience with hunting. I fired it from my 16/16 SxS on shooting range only.