Here's a lucky escape, from one of my case files.
A guy was walking along, minding his own business and was struck on the right side of the head in the temporal region by a bullet. He didn't see or hear where it came from, and it did not penetrate very deeply. He was not incapacitated in any way and arrived at hospital fully alert.
The radiographs reveal a bullet which is probably an FMJ, known to be deformed when you compare the AP view to the lateral. Look at the ratio between the height and width of the bullet on both radiographs. It is evident radiologically that the bullet has been flattened somewhat:
The bullet was palpable and was removed under local anaesthetic the same evening. Sure enough, it was a deformed FMJ with post-discharge rough striations on one side. What we have here is an errant shot which lost a lot of energy during a ricochet.
The temporal region of the skull is very thin. This bullet did not penetrate the bone, it was lodged in a subcutaneous position easily accessible in the ER.
The paperclip is a skin breach marker. One possible trajectory has the bullet coming from behind and above the victim. Even if it penetrated the brain, he would be unlucky to be killed, but would take frontal lobe damage. That relies on a big assumption that the trajectory stayed true and the bullet did not deflect off the inside table of the skull vault.
The point is, this bullet lost a lot of energy. If either the shooter or the victim was differently positioned, this could have been a complete miss or a fatality.
No two gunshot injuries are the same!