The three branches of ballistics
Ballistics is the science of a projectile in motion, and it splits into three stages. Internal ballistics is everything that happens inside the gun, from primer ignition to the moment the bullet leaves the muzzle. External ballistics is the flight through the air: gravity, drag, wind, and spin. Terminal ballistics is what happens when the bullet reaches its target.
Terminal ballistics is the only stage you can hold still and measure, and it is the one that decides whether a round does its job. It is also the only stage that happens inside something. That is exactly what clear gel is for: it makes the inside visible.
The five events, in order
1. Entry. The bullet meets the surface. A non-expanding bullet leaves a hole close to its caliber. An expanding bullet has barely begun to open at this point.
2. Wound path. The bullet travels a track through the medium. Handgun hollow points usually run fairly straight; high-velocity rifle rounds often yaw and tumble. The length of that track is the penetration depth.
3. Permanent cavity. The actual destroyed path the bullet leaves behind. It widens as a hollow point mushrooms. This is the primary wounding mechanism for handgun rounds, and in clear gel it stays visible and measurable.
4. Temporary cavity. As the bullet passes, it shoves material outward at high speed, then the medium snaps back. In clear gel that event is recorded permanently as radial fracture lines, so you can study it long after the shot. Organic ordnance gelatin has to be cut apart to see it. Clear gel does not.
5. Terminal position. Where the bullet stops and what it looks like. A clean mushroom means the round performed. An unopened bullet usually means the hollow point clogged. A pile of fragments tells its own story.
The three measurements that matter
Every gel test report comes down to three numbers, and a round has to hit all three at once.
| Measurement | What it is | Benchmark |
|---|---|---|
| Penetration depth | How far the bullet traveled before stopping | FBI: 12 to 18 inches |
| Expanded diameter | Final bullet width after mushrooming | At least 1.5x original caliber |
| Retained weight | How much bullet mass stayed intact | 85% or more |
A deep round that never expands makes a smaller hole than a shorter round that opens to twice its width. You only know which is which if you can see the whole wound profile, permanent cavity, temporary cavity fractures, recovered bullet, and depth, all at once. That is what clear gel shows and opaque mediums cannot.
See what you shoot.
Validate your carry or hunting load in the same calibrated gel the industry tests in.