Which of the following is NOT an individual characteristic of a firearm?

• A. Primer residue on cartridge
• B. Striations parallel to the lands and grooves
• C. Unique variations due to wear on the weapon
• D. Firing pin impression

Answer: (A)

Individual characteristics are the unique marks produced by a specific firearm’s components and its wear, which can be used to link a bullet or cartridge back to that exact weapon. The rifling inside a barrel leaves striations on bullets that, while subtle, are distinctive to a particular barrel and its condition. Firing pin impressions on a cartridge case are another clear example, created by the exact shape and wear of the firing pin in that firearm. Over time, the weapon’s use adds additional unique variations, reinforcing a match between the evidence and the gun.

Primer residue on a cartridge, on the other hand, is not generated by the firearm itself. It comes from the primer chemistry and can be transferred during handling or from different ammunition lots. While it can indicate that a cartridge was fired or handled in a firearm, it does not reflect anything unique about a specific gun and cannot reliably identify which firearm was used.