Well John, I can say of the Water Buffalo I shot with them (Woodleigh Hydro's), the wound channel was definitely large than the bullet diameter.

I also had a Hydro and a normal Woodleigh SN out of my 465 hit 4" or so apart and follow the same track across the body,
of course one 4" below the other. The SN stopped before exiting, the Hydro exited. The wound channels were very similar.

I've shot enough buffalo and cut up hundreds more to know what a good wound channel is and it is definitely their
in Red LOL.