It is becoming more apparent that cast bullets should not be too hard or they are brittle and can break up on solid bone, BHN of 25 has proven to be brittle and it is now accepted that BHN 19 or so is optimum for hardness, with little if any expansion, and much less chance of busting up due to brittleness. My experimenting shows that those figures are about right and that adding Tin is also great for keeping the bullet together on impact, it doesn't add much to the hardness, but adds to the ductile strength of the bullet. Most commercial outfits don't add tin because, you guessed it, it is fairly expensive. Instead the bullets get their hardness from antimony, which helps cause the shattering on impact. As a bonus, the slightly softer bullets usually shoot better!