Exploration of Breech Face Subclass Characteristics

Subclass characteristics are caused by damage, defects, and/or wear on a cutting tool that transfers to a small group of consecutively manufactured surfaces, but not all surfaces made by that tool. They are more distinctive than class characteristics, but unlike individual characteristics, they cannot be used to identify a cartridge case as having been fired by a particular firearm. Firearm examiners can mistake these subclass characteristics as individual characteristics, which can lead to a false identification.

The objectives of this study are to assess the production of subclass characteristics during the manufacturing of breech faces by three different methods, observe how well subclass characteristics persist on manufactured breech faces with and without any finishing methods, and observe the effect of the primer on the quality/quantity of the breech face impression. 

Upon completion of this webinar, attendees will learn:

1. How subclass characteristics are produced when breech faces are manufactured using a broach, lathe, and endmill.
2. The extent to which subclass characteristics persist on manufactured breech faces with and without any finishing methods.
3. The effect of the primer on the quality/quantity of the breech face impression.

Presenter:

• Veronica Franklin, M.S., Ph.D. Candidate at West Virginia University