Hello. Corbon's PowRball is an aggressive expander that still manages to get around 12" penetration in 10% ballistic gelatin. It does this because it takes 4 or 5" penetration for the bullet jacket to separate enough from around the polymer ball that forms the nose to allow the hydraulic forces to begin expanding the thinly jacketed bullet. I have not shot any living creature with PowRball. In wet pack and water, it has consistently expanded in 9mm and .45 ACP, which are the only calibers I've tried it in. One fellow I trust reported seeing it used on deer from a .45, but penetration was lacking and below the 12" in ballistic gelatin.
My limited experiences with the PowRball are just that, but I think it is probably a good defense load for folks concerned with overpenetration issues.
Here is what I do have:
http://www.hipowersandhandguns.com/CorbonPowRball.htm
Personally, I prefer the DPX line of Corbon ammunition.
Best.