Quantitative assessment of barrel wear from solid copper bullets.

Area of Science:

• Forensic Science
• Firearm and Toolmark Examination
• Material Science

Background:

• Firearm and toolmark identification relies on unique characteristics imparted by firearms onto ammunition.
• Barrel characteristics can change with use, posing challenges for forensic examiners.
• The impact of solid copper bullets on firearm barrels requires investigation.

Purpose of the Study:

• To assess the effect of firing 500 solid copper bullets on the rifling characteristics of a new Glock 19 Gen 5 pistol with a Glock Marksman Barrel (GMB).
• To determine if barrel erosion over 500 rounds affects the ability to identify a bullet to its originating firearm.

Main Methods:

• Collected 68 bullets (first 10, last 10, every 10th in-between) fired from a Glock 19 Gen 5 pistol.
• Generated 3D scans of land engraved areas (LEAs) using the Cadre Forensics Versa system.
• Analyzed striation profiles using Cadre Forensics' Congruent Matching Profile Segments (CMPS) algorithm and KPSS time series test.

Main Results:

• A statistically significant decreasing trend in CMPS scores (p < 0.01) was observed from bullet 1 to bullet 500.
• Visual comparisons and algorithm scores indicated erosion of barrel characteristics over 500 shots.
• Identification between the first and last bullets fired was deemed unlikely due to significant changes.

Conclusions:

• Solid copper bullets demonstrably erode barrel rifling characteristics after extensive use (500 rounds).
• The observed erosion can compromise the reliability of firearm identification, particularly when comparing ammunition from significantly different stages of barrel wear.
• Forensic examiners must account for the time elapsed between a shooting incident and firearm recovery, as barrel characteristics may change, influencing comparison interpretations.