Final answer:
Gunshot residue contains burned particles of primer powder, comprising various elements from the propellant and fire discharge during a firearm's operation.
Step-by-step explanation:
Gunshot residue contains burned particles of primer powder.
Gunshot residue (GSR), also known as firearm discharge residue (FDR), is the material that is expelled from a firearm when it is fired. It usually consists of burned and unburned particles from the propellant, which is often made from a mixture of substances such as gunpowder (historically), primer, and additional elements from the bullet and cartridge casing. When a gun is fired, high-pressure gases force the bullet out of the barrel, and the intense heat and pressure cause the primer to ignite, which in turn ignites the gunpowder. This ignition creates an explosion that propels the bullet forward, and simultaneously vaporizes the solid components of the cartridge, creating a plume of residue.
The composition of GSR can vary, but common elements include barium, antimony, lead, along with other metals that were part of the primer and bullet. The analysis of gunshot residue can be a crucial aspect in forensic investigations to determine whether a person has fired a gun or was in close proximity when a gun was fired.