I have some Underwood ammo using the Lehigh defense bullet for use in a couple of handguns. The one thing that's interesting about the bullet (to me) is that the head of it looks like a blunt Philips head screwdriver. I remember reading some data regarding one of the rounds, and the spin created by the barrel rifling is actually what makes it a very effective round. It essentially acts like a 63,000 RPM meat auger when it strikes, and since it's solid copper, it continues to bore and auger fairly deep into the target, making one heckuva wound channel.I am a fan of Underwood. That said, I'm not sure that on a black bear, hog or deer that the Lehigh bullets would work any better than an appropriate hard cast (which they coat with a proprietary coating) or even good SP bullet. My observations are that they are also much more pricey as well.
The imagery from that description always stuck with me, and it's my primary personal defense choice in the winter months when I don't want a hollow point getting plugged up by outerwear and not penetrating enough to stop a threat. I suspect that it would perform incredibly well on larger game for the same reason, particularly if you use or load up one of the heavier 305 grain Xtreme Penetrator bullets. I'd sure as shyte hate to get shot with one!