Bullet Fingerprinting Instant

As a bullet travels through a gun barrel, it is gripped by —spiral grooves machined into the metal to make the projectile spin for stability.

Unlike human fingerprints, a gun's "fingerprint" changes over time. Every shot fired slightly alters the microscopic striations in the barrel. Experts may only fire a limited number of test rounds because the fifth shot might already look different from the first. 2. Success Rates and "Expensive Failures" bullet fingerprinting

: The raised parts of the rifling (lands) and the cut-out parts (grooves) leave parallel scratches on the bullet. As a bullet travels through a gun barrel,