Standing Wolf,
The reversed HBWC's do indeed expand at low (~700fps) velocities.
At least, in wet newsprint they do.
Some that I've recovered, fired from a 2" M10, a 3" M64, and a 4" M15 all expanded from .650-.795", which ain't bad, nearly all doubling their diameters.
They didn't really "mushroom" as a faster round may have, but instead they resemble top hats like magicians wear, the expanded 'rim' didn't peel back against the body of the bullet, but just bent out to 90 degrees.
Penetration was about 4-6" in the newsprint.
And retained weight was on the order of 125-140gr's.
I don't think I'd choose these loads for street defense, but there is no doubt in my mind these would be good around the camp and farm for skunks, raccoons, bad dogs and other small-to-medium sized four legged miscreants.
Energy dump is absolute, and along with that lack of overpenetration comes safety for nearby livestock, barn interiors, camping supplies, fire rings, etc.
They are nice and accurate, at least out to about 20yds before they tumble, and recoil is not relevent.
Fun little loads to play with, that's certain.
-Kframe