The energy transfer theory is called hydrostatic shock, think of a pebble being dropped into a pool of water and the small waves radiate away from the impact point. The theory was that these "waves" would impact nerves with enough force that a trauma message would be sent to the brain and the brain would, as a safety mechanism, tell the body to lie down. After the Miami FBI gunfight as previously mentioned the bullet makers went to work on bullet design, they wanted to make a bullet that was more reliable in various mediums. They tested the bullets in ballistics gel and used high speed cameras to capture what the bullet did at different points in the gel. Some, seeing the effect of the "temporary wound cavity" ran with hydrostatic shock as the be all and end all of the mythological term "stopping power". Lot's of magic bullets have been sold on the strength of a myth. Ballistics gel does not now and was never supposed to replicate human tissue. Simply put, all bullets fired from commonly carried hand guns suck, people that don't want to fight will give up or run away and people that do want to fight will keep fighting until they lose consciousness from blood loss.