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Inspection
After processing oils are removed, the case must be inspected. The physical dimensions are checked against engineering specifications. Some cases may be set aside for grain structure evaluation and/or micro-hardness testing.
This test requires the following:
- Sample cases are sectioned and the cut surfaces polished.
- The polished surface is etched in acid to define the grain boundaries.
- The average grain size is measured, using a microscope with a calibrated eyepiece.
- A hard, sharp point is pressed into the metal with a known amount of force, leaving a tiny, diamond-shaped impression.
- The metallurgist measures micro-hardness using a microscope. The dimensions of the impression are measured; the smaller the impression, the harder the brass.
Some cartridge cases are nickel plated for appearance and/or corrosion resistance. Cosmetic plating is performed after all heat treating is completed and usually accomplished after passing inspection.
Additional Online Courses
- What Every First Responding Officer Should Know About DNA Evidence
- Collecting DNA Evidence at Property Crime Scenes
- DNA – A Prosecutor’s Practice Notebook
- Crime Scene and DNA Basics
- Laboratory Safety Programs
- DNA Amplification
- Population Genetics and Statistics
- Non-STR DNA Markers: SNPs, Y-STRs, LCN and mtDNA
- Firearms Examiner Training
- Forensic DNA Education for Law Enforcement Decisionmakers
- What Every Investigator and Evidence Technician Should Know About DNA Evidence
- Principles of Forensic DNA for Officers of the Court
- Law 101: Legal Guide for the Forensic Expert
- Laboratory Orientation and Testing of Body Fluids and Tissues
- DNA Extraction and Quantitation
- STR Data Analysis and Interpretation
- Communication Skills, Report Writing, and Courtroom Testimony
- Español for Law Enforcement
- Amplified DNA Product Separation for Forensic Analysts