Gun powder residue can stay on the hands for as long as you stay without washing your hands. The powder can stay for hours and even days after you have fired the gun. Once you wash your hands, the powder is completely washed away by water.
1 year ago
Last edited at 3:15PM on 6/7/2012
Not very long. Studies have shown that a hard slinging or shaking of the hand will scatter some of the particles. If the hand is rubbed against clothing or wiped with a towel, there’s a good chance that most, if not all, gunshot residue will come off the hands. If the hands are washed, GSR is most likely gone.