At magnum revolver velocities, I have not encountered any alloy that will not nold together well at any speed it can be driven accurately without leading. Pure lead or other very soft alloys cannot be driven fast enough to get certain expansion, nor to tear them to pieces.
High ductility is mandatory to prevent bullet breakup at higher speeds of 2200 + fps. i.e. Low antimony heat treated to get hardness high as possible.Wheel weight alloy, hardened, is as good as it gets, and that certainly isn't an expensive alloy!