Penetration is the critical factor when selecting a round for large game. This is the same reason that heavy rifles for African dangerous game like the 577 Nitro Express, the 460 Weatherby Magnum, etc most often use a solid bullet like those made by Barnes. Since the bullet doesn’t expand and it holds together properly, the highest velocity yields the best penetration. However the rules change with expanding bullets. Manufacturers design a bullet jacket to perform within a specific velocity range. Go slower or even faster than the design limits, the penetration is usually less. I took a 165 bullet and shot it out of a .308 Winchester and a .308 Norma Magnum. The Norma hit the wet catalogs in spectacular fashion and tore a huge hole but the Winchester actually drove a small hole deeper as it expanded slower so it was not pushing as much surface area.
Well to use the same principle for handguns the fastest is not always the best for penetration. I would do some testing with various velocities using a controlled expanding bullet like the Hornady XTP or a cast bullet. The term hard cast can be misleading as well. I once lost a silhouette pistol match because my cast bullets had so much antimony in them to make them hard so I could shoot them faster but they shattered on the ram and would not knock them down. Good cast bullets should be in the Brinell Hardness 15 – 16 range, lower or higher is not better. Go for penetration first, accuracy second and velocity third. Just my 2 cents and I hope this helps.