Answer: A few hours
Explanation:
A gunshot residue is a powdery discharge of a firearm which consists of unburned or partially burned primer and propellent mixers which are used in the cartridge case to propel out the projectile with force exerted by the gases produce after burning of the powder charge. This residue gets deposit over the hands of the shooter, clothes of the shooter or the target and the nearby firing region.
The gunshot residue remains for few hours on a shooter's hand. The powder discharge can easily be cleaned and this can be collected by using tape, swabing or by washing the hands with suitable solvents.
