Reply #23: Which doesn't answer the question...

[JackRiddler]

Powder burns....

or tattooing, begin to occur as the gun is backed up to more than 1/2" from the body. The maximum distance from which powder burns can occur depends a good deal upon the type of gun used.

Powder burns

are orange brownish reddish in appearance. If they are gray or yellow, the victim was already dead when the shot was inflicted. Powder burns are caused by burning particles of powder which are ejected from the gun and become imbedded into the live skin. There is no actual burning of the skin which takes place. In that sense, the name powder burn is a misnomer. The particles simply penetrate into the skin and finish burning there by themselves. At closer than 1/2", the powder grains do not have a chance to spread out behind the bullet. They go into the entry wound rather than tattooing the skin around the entry wound.

http://dmmoyle.com/simeans.htm

Iver Johnson .22 caliber: at what distance is it likely to produce powder burns? .22 caliber in general?

Since you're citing wikipedia, what the hell, I'll do the same (possibly my first cite of it ever):

In conducting an autopsy on Kennedy, Los Angeles coroner Thomas N. Noguchi found powder burns on Kennedy's ear and gunpowder residue in his hair. Noguchi said this indicated that Kennedy was shot from a distance of, at most, 1.5 inches. (When a firearm is discharged, the powder travels only a few inches because the gas is very light.) Noguchi's conclusions led to speculation that Sirhan was too far from Kennedy to have adminstered the fatal shot, and that a second shooter must have been present. Noguchi himself wrote years later that "Until more is precisely known…the existence of a second gunman remains a possibility. Thus, I have never said that Sirhan Sirhan killed Robert Kennedy."(4)

http://en.wikipedia.org/wiki/index.php?title=Robert_F._Kennedy_assassination&oldid=13754833