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Firearms Ballistic Pathway

Run the Ballistic Pathway MicroSim Fullscreen

About This MicroSim

A bullet's journey has three phases, and each one leaves its own kind of forensic evidence:

  • Internal — everything that happens inside the firearm: the barrel engraves rifling marks on the bullet, the breech face stamps the cartridge case, and gunshot residue (GSR) is created.
  • External — the bullet's flight through the air, described by its trajectory angle.
  • Terminal — the impact with the target, which produces entry and exit wounds with different shapes.

This MicroSim lays the whole pathway out as one annotated diagram so you can identify each piece of evidence and learn how examiners collect it.

How to Use It

  1. Click any blue evidence label — Rifling marks, Breech face impression, GSR emission, Trajectory angle, or Wound characteristics. A panel opens telling you what it is, when it is produced, and how it is collected.
  2. Click the entry or exit wound on the target to compare their shapes.
  3. Hover the barrel cross-section (or tick Animate rifling) to watch the lands and grooves spiral — the diagram lists the class characteristics (6 lands & grooves, right twist).
  4. Use the dropdown to jump to any item, and Reset to clear the panel.

What You Can Learn

  • Identify the three ballistic phases: internal, external, and terminal.
  • Match each phase to the evidence it produces.
  • Describe what each evidence type is, when it forms, and how it is collected and analyzed.

You can embed this MicroSim on your own web page with this iframe:

<iframe src="https://dmccreary.github.io/forensic-science/sims/ballistic-pathway/main.html"
        width="100%" height="512" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 10–15 minutes Bloom level: Remember (L1) — identify.

Warm-up. Ask: "Where does a bullet pick up the marks that tie it to one specific gun?" Then have students click each evidence label and sort the five items into the three phases.

Guided questions:

  • Which two evidence types are individual characteristics (unique to one firearm), and which are class characteristics (shared by many)?
  • Why does GSR appear in the internal/muzzle phase but not the terminal phase?
  • How do the entry and exit wounds differ, and why does that difference reveal the bullet's direction of travel?

Extension. Discuss why class characteristics narrow the field of possible firearms while individual characteristics can identify a single weapon.

References

Specification

This MicroSim was generated from a specification in Chapter 13: Firearms, Ballistics, and Toolmark Examination.

Design note: the firearm, trajectory, and target are stylized for teaching, not anatomically or mechanically exact. The interaction is click-to-identify (Remember level): each evidence label opens a definition and collection procedure rather than running a physics simulation.