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Objective evaluation of consecutively manufactured Glock Marksman Barrels using EvoFinder®
Jack McKeon1, Erich Smith1, Rachael Gominsky1
1FBI Laboratory, Firearms/Toolmarks Unit, Quantico, Virginia, USA.
Journal of Forensic Sciences
|March 13, 2026
Summary
Glock Marksman Barrels (GMBs) feature a new rail component. This study found that subclass carryover on GMB rails does not cause false positives in firearm identification, ensuring reliable toolmark analysis.
Area of Science:
- Forensic Science
- Firearm Examination
- Manufacturing Processes
Background:
- Glock Marksman Barrels (GMBs) incorporate an additional rail component into their polygonal rifling.
- This innovation has sparked debate among firearm examiners regarding its impact on identification accuracy.
Purpose of the Study:
- To investigate the manufacturing of GMBs, specifically focusing on subclass characteristics and striation variations.
- To determine if the added rail component aids or hinders microscopic comparisons by firearm examiners.
Main Methods:
- Information on GMB manufacturing was gathered from Glock engineers.
- Microscopic evaluation of casts from consecutively manufactured GMBs identified repeating patterns due to subclass carryover.
- Toolmarked surfaces of bullets fired from 10 consecutively manufactured GMBs were scanned into the EvoFinder® system for objective analysis.
Main Results:
- Repeating patterns were observed on GMB rails, attributed to mandrel manufacturing and subclass carryover.
- Objective evaluation using the EvoFinder® system demonstrated that subclass carryover did not impede bullet-to-barrel assignments.
- Inclusion of N-max criterion in scoring enabled complete separation of distributions, confirming reliable identification.
Conclusions:
- Subclass carryover on GMB rails does not lead to false positives in firearm identification.
- The additional rail component does not hinder, and may potentially aid, examiners in microscopic comparisons.
- The study validates the reliability of GMBs for forensic firearm examination.
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