There's really no way to relate rifling/etc to a specific gun. Unless it was forged in some bespoke process that can also be accessed and replicated the rifling pattern will look like 100,000 different guns. Other analysis is also bunk (blood spatter, gunpowder stuff, etc). Ammo matching can provide circumstantial evidence but is likely defeated by just shutting your mouth.
Most criminals subject to this are probably caught because they loaded the magazine without gloves and left a fingerprint on the casing that gets completely etched into it on firing. Or, you know, police do actual police work and pressure the right people into narc'ing on the suspect.
Most criminals subject to this are probably caught because they loaded the magazine without gloves and left a fingerprint on the casing that gets completely etched into it on firing. Or, you know, police do actual police work and pressure the right people into narc'ing on the suspect.