Why is it breech face mark is considered realable?

The breech face mark is considered reliable because it reflects unique and consistent impressions left on the cartridge case by the firearm's breech face during firing. These marks are influenced by the specific design and wear characteristics of the firearm, making them distinctive to each weapon. Firearms experts can analyze these markings to link fired cartridge cases to a particular gun, thereby aiding forensic investigations in determining the firearm used in a crime. Additionally, the permanence of these marks allows for reliable comparisons over time.