1. Firearms Identification

2. Forensic firearms examinations identification of a bullet, cartridge case, or other ammunition component as having been fired by or in a particular firearm. identification of a bullet, cartridge case, or other ammunition component as having been fired by or in a particular firearm. the possibility for such singular identification can be attributed to specific machining processes used in the manufacture of firearms. the possibility for such singular identification can be attributed to specific machining processes used in the manufacture of firearms.

3. Rifling Helical grooves (rifling), cut into the bore of a barrel of a firearm during production, increase the accuracy of that firearm Helical grooves (rifling), cut into the bore of a barrel of a firearm during production, increase the accuracy of that firearm Effects: Effects: Spin Spin Stabilized Stabilized Marks on the bullet (lands and grooves) Marks on the bullet (lands and grooves)

4. A rifled barrel: will contain scratches, scrapes, and other minute nicks and flaws will contain scratches, scrapes, and other minute nicks and flaws exacerbated through the subsequent use and discharge of the firearm exacerbated through the subsequent use and discharge of the firearm or as a result of natural wearing processes such as rusting and corrosion or as a result of natural wearing processes such as rusting and corrosion bullet will have unique microscopic markings as a result bullet will have unique microscopic markings as a result

5. Firing pin impressions: During the discharge of a firearm, the firing pin strikes the primer of a cartridge, creating microscopic contact marks and unique indentations. During the discharge of a firearm, the firing pin strikes the primer of a cartridge, creating microscopic contact marks and unique indentations.

6. Breechface impressions: As the powder within the cartridge begins burning, the cartridge case is propelled backwards against the breechface with enough force to be impressed with the characteristic microscopic features of that surface. As the powder within the cartridge begins burning, the cartridge case is propelled backwards against the breechface with enough force to be impressed with the characteristic microscopic features of that surface.

7. When no firearm is recovered: rifling parameters taken from the recovered bullets can be used to determine the possible manufacturers of the firearm from which the bullets were fired. rifling parameters taken from the recovered bullets can be used to determine the possible manufacturers of the firearm from which the bullets were fired. General rifling characteristics or GRC are the identified rifling pattern (i.e. 8/right) and the diameters of the individual lands and grooves. General rifling characteristics or GRC are the identified rifling pattern (i.e. 8/right) and the diameters of the individual lands and grooves. Using these parameters, firearm examiners can search through a database of known rifling data. Using these parameters, firearm examiners can search through a database of known rifling data.

8. A typical GRC search: a 9mm LUGER bullet, fired from a 6/right rifled barrel, with a land width of.055 and a groove width of.125. a 9mm LUGER bullet, fired from a 6/right rifled barrel, with a land width of.055 and a groove width of.125.

9. Results of Search: CARTRIDGEMANUFACTURERTWISTL&GLAND GROO VE 9MM LUGERAA ARMS INCR 6.055.120 9MM LUGERASTRAR6.053.128 9MM LUGERBERETTAR6.055.130 9MM LUGERHI-POINT FIREARMSR6.055.120 9MM LUGERINTERDYNAMICR6.055.124 9MM LUGERLLAMAR6.054.120 9MM LUGERMAUSERR6.054.128 9MM LUGERSMITH & WESSONR6.056.122 9MM LUGERSTARR6.054.126 9MM LUGERSWD INCR6.055.120

10. FBI Database: The database used by firearm examiners all over the world is compiled and maintained by the FBI. The database used by firearm examiners all over the world is compiled and maintained by the FBI. The FBI has been recording rifling data from firearms for over 20 years. The FBI has been recording rifling data from firearms for over 20 years. As new firearms are manufactured, the rifling data is included in the database. As new firearms are manufactured, the rifling data is included in the database.

11. Case Study Many years ago, a double murder occurred in our community. An elderly couple was found shot to death in their home by their son. Many years ago, a double murder occurred in our community. An elderly couple was found shot to death in their home by their son. It appeared from the scene that there had been a break-in but the son was immediately a suspect. Investigators had a feeling that the son may have committed the crime but could not determine if he had owned or had access to a firearm. It appeared from the scene that there had been a break-in but the son was immediately a suspect. Investigators had a feeling that the son may have committed the crime but could not determine if he had owned or had access to a firearm. Bullets from the scene were examined and it was determined that they were of 38 caliber and were fired from an 8/right rifled barrel. Bullets from the scene were examined and it was determined that they were of 38 caliber and were fired from an 8/right rifled barrel.

12. Case Study A list of manufacturers was compiled and given to the investigators. A list of manufacturers was compiled and given to the investigators. Using this list, the investigators searched a weekly "Bargain Mart" classified ad publication. By calling the ads for firearms included on the list of possibilities, the investigators found one individual who said he had sold his revolver to an individual who matched the description of the son. Using this list, the investigators searched a weekly "Bargain Mart" classified ad publication. By calling the ads for firearms included on the list of possibilities, the investigators found one individual who said he had sold his revolver to an individual who matched the description of the son. The son was then picked out of a police line-up by the individual who had sold him the gun. When confronted with the evidence the son confessed to the killings. The son was then picked out of a police line-up by the individual who had sold him the gun. When confronted with the evidence the son confessed to the killings.