If it expands up to .50, you're saying that it is the lethal equivalent of an unexpanded .45 ACP. Except that it creates a smaller entry wound, and it's depth of penetration is either the same or less than .45 FMJ.
How great does that sound?
And that's only if you can come up with a bullet design that will reliably expand at those velocities without fragmenting. With half the starting frontal area of a .45 and 72% the frontal area of 9mm, you have much less hydraulic area to expand the bullet. This is velocity range is another limbo, between where traditional pistol hollowpoints become either too fragile or under penetrate, and rifle velocities and weights where you switch over to tougher spitzers and soft points.
If you go down to smaller bullets, you can more predictably get them to tumble. But a .30 bullet at these velocities isn't going to expand much and is too heavy to yaw much either.