Gotta throw something in here... much of the permanent wound cavity of 2000+ fps rifle rounds comes from fragments rotating into the wound/lacerating it as the stretch occurs. The same effect can be seen from yawing rifle bullets and particularly those which eject fragments from an open base or break apart at the cannelure. I discussed this with Fackler at some length years ago when we used him as an expert witness on multiple shooting/homicide involving a rifle. It is also evident in radiology of those wound types as well as Fackler's own diagrams of rifle wounds.
![[Linked Image]](http://ciar.org/ttk/mbt/papers/misc/paper.x.small-arms.wounding-ballistics.patterns_of_military_rifle_bullets.fackler.unk_files/wund6.gif)
Like many tissues in in living organisms, it is is the nature of gelatin to stretch significantly and close up behind the wounds. The stretch you're observing from these Phillips bullets and the permanent cavity left in its wake, bears no resemblance to those caused by rifle service rounds, much less expanding rifle rounds.
