Where is gunshot residue (GSR) projected from a firearm?

Gunshot residue (GSR) is produced during the firing of a weapon and can be expelled from various openings in the firearm. When a gun is fired, the explosion in the chamber generates high-pressure gases that force not only the bullet but also tiny particles (composed of materials like lead, barium, and antimony) out of the firearm.

These particles can be projected from several areas: the muzzle, where the bullet exits; the ejection port, where spent casings are expelled; and any other openings, such as gaps in the firearm’s construction. This is why the correct answer indicates that GSR can come from any opening in the firearm.

Understanding this concept is crucial in forensic investigations because it helps to determine if a suspect may have recently discharged a firearm. The presence and location of GSR can provide significant evidence in criminal cases, influencing investigations and potential charges.