Modern methods of firearms identification are highly scientific techniques which require the use of comparison microscopes and other laboratory apparatus. When a firearm is fired, the distinctive markings made on projectiles or cartridge cases, furnish reliable evidence which may be used in court. The identification of a firearm as having fired a particular projectile or cartridge case is based on the fact that the barrels of weapons are machined and microscopic irregularities in the tools cause minute scratches and irregularities on the surface of the barrel. In addition, subsequent wear, use, rust and corrosion add to the markings. THEREFORE, A PROJECTILE FIRED THROUGH A BARREL WILL HAVE, ENGRAVED ON ITS SURFACE, THE INDIVIDUAL CHARACTERISTICS OF THAT BARREL, AND NO OTHER.