No rifle hunting bullets that I am aware of require five inches of penetration to expand. Instead most expand fully within their own length, which israrely as much as two inches. The exceptions are "closed hollow points" like the Berger hunting bullets, which penetrate around 2" before the front end collapses and they start to expand.
This is why the area immediately behind and around the entry is most damaged: That's where the bullet totally expands. This has been proven many times in several kinds of media, and duplicated in extensive test-shooting of big game.
Lots of them do at lower impact velocities. In any case, you might google “Buford Boone terminal ballistics”...
