I did not try buffalo horn but cow (zebu) horn. Tu cut a slab in half I just put it in the vise and cut it with the metal hacksaw, making sure to start the cut in the middle and not at an angle. Worhed perfect, they came out nearly flat, had to sand them just a few minutes on a flat surface to get them true flat. I've learned a thing though. When you are past halfway you need to loose the vise a bit or the hacksaw blade will jam.
Hope it helps.