Terminal Ballistics 101
Everything that happens when a bullet reaches its target — and why clear gel is the only way to see all of it.
The Three Branches of Ballistics
Ballistics is the science of projectile motion and impact. It's divided into three distinct stages — and if you're reading this guide, you're interested in the third:
- Internal Ballistics — What happens inside the firearm when a round is fired: propellant burn rate, pressure curves, barrel harmonics.
- External Ballistics — The projectile's behavior in flight: trajectory, drag coefficient, BC, wind drift, velocity drop at distance.
- Terminal Ballistics — What happens the moment the bullet contacts a medium: penetration depth, expansion, fragmentation, energy transfer, wound channel geometry.
Terminal ballistics is the stage that determines real-world effectiveness — whether for hunting, defensive use, law enforcement, or military applications.
The Five Events, In Order
- Entry — The bullet meets the surface of the medium. Resistance begins immediately. Jacketed bullets typically remain intact; unjacketed or soft-point bullets begin deforming on entry.
- Wound Path — The projectile's track through the medium. Clear gel lets you see this path in 3D, preserved in the gel after testing — unlike opaque alternatives.
- Permanent Cavity — The physical tunnel left behind by the projectile. For expanding bullets, this grows as the nose expands. For FMJ rounds, it's roughly the bullet's diameter.
- Temporary Cavity — The radial wave of energy that expands outward from the wound path, then collapses back. In clear gel, this is visible as fracture lines extending from the permanent cavity. This is unique to synthetic gel — opaque gelatin can't show it.
- Terminal Position — Where the projectile comes to rest. The final position, orientation, and condition of the bullet are critical data points for load selection.
The Three Measurements That Matter
| Measurement | What It Tells You | FBI Minimum (Handgun) |
|---|---|---|
| Penetration Depth | How far the bullet traveled through tissue analog | 12 inches (305mm) |
| Expanded Diameter | How much the nose expanded relative to original diameter | 1.5× original caliber |
| Retained Weight | What percentage of the original bullet weight remains | ≥ 85% |
The FBI's 12-inch minimum penetration standard is based on the distance from the skin surface to the human body's vital organs through the thickest anatomical cross-sections.
Organic gelatin requires refrigeration, degrades within hours, and is completely opaque — you see entry and exit, nothing in between. Clear Ballistics synthetic gel eliminates all of these problems. The temporary cavity, wound path fracture lines, and terminal projectile position are all visible from any angle, preserved in the block indefinitely, and photographable or filmable without destructive examination.
10% vs 20% — Which Standard Applies?
The formulation you choose depends on the test standard you're working toward and the caliber you're testing:
- 10% Gel (FBI Standard) — Handgun calibers, pistol-caliber carbines, personal defense loads. FBI's 12–18-inch penetration standard was developed using 10% gelatin.
- 20% Gel (NATO Standard) — Rifle calibers, high-velocity rounds, military and hunting ammunition. The denser medium produces more accurate terminal data for high-energy projectiles.
See What You Shoot
Validate your carry or hunting load in FBI-calibrated clear gel. Ships next business day.