At around 18-24 inches most firearms will start to deposit considerable concentrations of gunshot residues that may or may not be visible to the eye. At distances of less than around 12 inches heavy concentrations of visible gunshot residues will normally be deposited. Visible gunshot residues around bullet entrance hole. A very intense deposit of gunshot residues will be found around the margins of a contact or near contact entrance hole. Contact gunshot entrance hole.
Gunshot residue is normally a combination of gunpowder residues and lead residues .
I say normally because some newer ammunition is virtually lead-free. More and more ammunition manufacturers are using lead free or low lead propellants because of the toxicity of lead. Gunpowder residue can contain unburned gunpowder particles, partially burned gunpowder particles or the carbonaceous soot from completely burned gunpowder. The image below show a bullet hole surrounded by gunpowder particulate residue. Gunpowder particulate residue around bullet entrance hole.