This photo shows a gunpowder burn on the inside of a skull.  This occurs when the gun is extremely close when fired.

Photos courtesy of OsteoInteractive at http://www-medlib.med.utah.edu/kw/osteo/index2.html

This photo shows a gunpowder burn to the soft tissue surrounding a gunshot wound.  These types of burns are also caused by the closeness of the gun to the victim when the gun is fired.  In this instance, the gunshot wound was to the neck, right under the chin.  If you look carefully you can see the muzzle slide/slide/slide guide rod impression when compared to the gun responsible for the injury (shown to the left).


Photo courtesy of Gerberth, centerfold