Any bullet that penetrates the central nervous system with sufficient force to damage it both structurally, as well as fatally, is a good bullet. And any bullet that can penetrate cross-ways from one side to the other of a large animal, laying waste to the lungs and rapidly depressurizing the lung cavity while exiting, is a good bullet.
Hard-cast or an A-Frame, it is the result that counts. So go forth and make results happen that we can all agree upon. The animal you hunt deserves a humane and relatively quick demise.