Agreed. Cast bullets are the limiting factor. But who says that more and more velocity is warranted? If dead is dead, then what more is needed? If the central nervous system is broken, the effects will be at that instance. If the lungs are punctured all the way through, then "ropes" of blood will pour out from both of the entrance and exit holes, drilled through the rib-cage as the animal bounds away. Just as excessive bullet weight adds nothing to killing power when taken to the extreme. The 700 grain 500 Smith and Wesson magnum load comes to mind here. The addition of more and more velocity reaches diminishing returns.