Introduction to Firearm Operating Systems

This 4-hour online course provides a foundational understanding of how modern firearm operating systems function. Designed for forensic firearm examiners seeking a deeper, systems based understanding of firearm operation as it relates to evidence interpretation and laboratory analysis. The course focuses on the mechanical function of firearm operating systems and how these mechanisms influence the generation of class and individual characteristics observed in casework. Participants will review and compare major operating systems including bolt-action, blowback, recoil-operated, and gas-operated designs with emphasis on how each system affects the cycle of operation and corresponding toolmark production. The course connects mechanical operation with forensic application, highlighting how operating system design can impact firing pin impressions, breechface marks, extractor/ejector marks, and various other marks. Key topics include: - Detailed cycle of operation and timing across firearm platforms - Mechanical sources of class vs. individual characteristics - Influence of operating systems on toolmark formation - Manual and automatic systems - Considerations for function testing and laboratory documentation The course uses diagrams, animations, and case-based examples to connect mechanical function with observed forensic evidence. By the end of the course, participants will be better equipped to relate firearm operating mechanisms to toolmark evidence as well as strengthen their ability to conduct examinations, interpret findings, and articulate conclusions in reports and testimony.