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. Modern smokeless gunpowder, and black powder, contains nitrate compounds.
Smokeless powders can either be single based or double based .
When either of these types of gunpowder burns the residue left behind will be in the form of a nitrite -based compound. Nitrite particles when emitted from the muzzle of a firearm will strike a nearby target and either be imbedded in the target's surface or leave a deposit of nitrite residue. Lead residues will be in a vaporous or particulate form and can come from a couple sources within a discharged cartridge. The most common source is the primer. Primers are used to start the ignition process in cartridges and commonly contain lead styphnate, barium nitrate, and antimony sulfide compounds.