If a firearm is submitted to the BCA, a firearm examiner must test fire the firearm to collect fired bullets and/or fired cartridge cases. They compare the test fired specimens to the bullets and cartridge cases collected at a scene.
Creating quality test specimens is important to successful microscopic comparative examinations
. By selecting proper ammunition, examiners can improve their ability to recognize matching features on the specimens. The BCA has an ammunition reference collection that houses a variety of calibers, cartridge types and bullet styles and weights for handguns, rifles and shotguns.
Firearm examiners must recover fired bullets for comparison to evidence bullets. The BCA has a water trap and cotton trap for recovering fired bullets. The examiner will consider many factors including bullet velocity and construction when choosing the appropriate recovery method.