A couple of thoughts on testing and measuring recovered bullets..........expansion rings were mentioned, which describe the ring of metal left after the bullet has expanded and the core has pushed past the ring. I don't see that as a failure, though some folks do. The softness of the alloy allows it to expand well, but the weight of the core allows momentum to drive it past the ring.......I see that as a good thing. In stiffer test media like wetpack and duxseal (stiff oil-based clay) expansion rings are more common, in ballistic gel less so. In human tissue who knows, it would matter more where the bullet impacted, i.e., abdomen or ribcage, spine or liver.
Some folks measure the diameter of the recovered slugs and compare the numbers, I do not. If the expanded section of the bullet has curled around behind and under the core, then maximum expansion was obtained BEFORE the bullet stopped, and comparisons are invalid. If bullet A stops before the petals are folded back, and bullet B does not, which is better? The measure of expanded diameter doesn't tell the whole story.
As much as I like the Critical Defense ammo from Hornady, it tends to be light-for-caliber, and I tend to prefer heavy bullets. You don't know whether you might be attacked by a 120-pound crackhead or a 375-pound biker, so you'd better have ammunition that will work on both. A lighter bullet generally won't penetrate as well as a heavier one, though lighter bullets go faster and expand more readily. Like everything else, it's a compromise, but I'll err on the side of penetration just in case the 375-pounder is the guy I'm dealing with. In summer it matters less, as there is less clothing to penetrate, but in wintertime I'll opt for the heaviest bullet that expands at the velocities it can achieve from the gun I'm carrying.
