Ballistic fingerprinting involves the study of firearms and the projectiles (bullet) that are discharged from them.
In present day, this is a very important area of forensic study as the amount of guns and shootings which take place seem almost commonplace.
The intention is to analyze the firearm to the most minute details in order to determine if a bullet which was fired came from that specific firearm which is being analyzed. It is believed that each gun which is built has differences which will be reflected on the bullet which is discharged.
Grooves or wear in certain areas of the barrel may leave tell tale markings on the fired ammunition. Rifling within a barrel ( spiraled lines which are inside the barrel. They help to spin the bullet when fired so it is more accurate in hitting the target aimed at) leave markings called striations on the bullet. The barrel may have slight nicks or markings which will leave more specific marks on the fired bullet or alter the striations almost like a fingerprint.
Each gun manufacturer will have differences in the way that they design their barrels and rifling patterns. They may have more rifling / spiraling lines, the lines may be closer together, they may twist more tightly than others, may spiral in a different direction etc....
As a recovered bullet is examined, it can be determined to have certain characteristics which would indicate if the bullet came from a specific brand/ gun manufacturer. From there, an examiner would attempt to discover the more specific or unique tell tale signs or marking which would help to determine and match the bullet to the specific gun used.
For example, if a bullet showed certain class characteristics of a Beretta, ( characteristics known to a specific manufacturer) , than the examiner would know that the bullet was shot using a beretta. They would now be able to ignore all other brands of guns and just focus on berettas, looking now for individual characteristics to match the specific beretta.
In this way, examiners can hopefully match up a fired bullet with the gun that discharged it.