Ballistic gel is a translucent, tissue-simulating material used primarily to test what bullets, projectiles, and protective equipment do on impact. It was developed to replicate the density and resistance of human muscle tissue, giving researchers a consistent, repeatable way to study how objects behave when they strike a body. While firearms testing remains its most well-known purpose, ballistic gel has expanded into body armor certification, forensic investigation, and even medical training.
How It Simulates Human Tissue
The standard formulation is a block of animal-derived gelatin mixed with water at a specific concentration. The most common version, established by military and forensic researchers, uses 10% gelatin stored at 4°C (about 39°F). At that ratio and temperature, the gel resists penetration in a way that closely matches human muscle. More specialized versions adjust the recipe for different tissue types. One study found that a blend of 0.35% agarose and 29.5% gelatin produced resistance values of 364 newtons, compared to 399 newtons for actual muscle tissue, making it a close biomechanical match for bone fracture research.
Newer synthetic alternatives have also entered the market, including gels made from styrene-ethylene/butylene-styrene (SEBS) polymers. These synthetic blocks don’t require refrigeration and can be reused, which makes them practical for repeated testing. Traditional gelatin blocks, by contrast, are single-use for ballistic impacts but have a shelf life of more than three years and can be stored at room temperature almost indefinitely before preparation.
Bullet and Ammunition Testing
This is the most common use. Ammunition manufacturers and law enforcement agencies fire rounds into calibrated gel blocks to measure how a bullet performs after it hits a target. The gel is translucent, so researchers can use high-speed video to capture the entire event in real time: the bullet entering, the temporary cavity expanding outward, and the cavity collapsing back. After the shot, the block preserves a permanent wound track that can be physically dissected, photographed, X-rayed, or CT-scanned to measure penetration depth, cavity size, and fragmentation patterns.
Two things matter most in these tests. The temporary cavity shows how much the surrounding tissue would stretch on impact, which relates to tissue damage beyond the bullet’s direct path. The permanent cavity reveals the actual channel the bullet carved, including any fissures radiating outward. By comparing these wound profiles across different ammunition types, testers can evaluate which rounds expand reliably, how deep they penetrate, and whether they fragment. Ballistic gelatin has become the standard method for this kind of terminal ballistic testing worldwide.
Before any of this testing begins, the gel block itself has to be certified. The FBI protocol requires firing a steel BB (0.177 inches in diameter) at 590 feet per second, plus or minus 15 fps. The BB must penetrate between 7.5 and 9.5 centimeters into the block. If the penetration falls outside that window, the block is considered unreliable and gets discarded. This calibration step ensures every test result is comparable across different labs and sessions.
Body Armor Certification
When a bullet hits a vest and doesn’t go through, the impact still transfers energy to the wearer’s body. That inward push creates what testers call a “back face signature,” essentially a bulge on the body side of the armor. Measuring that bulge tells engineers how much blunt trauma the wearer would experience even from a stopped round.
Traditionally, body armor testing in the U.S. and U.K. has used a modeling clay called Roma Plastilina No. 1 as the backing material. The armor panel sits against the clay, a round is fired, and the dent left in the clay is measured. But researchers have been comparing this approach against 10% ballistic gelatin and synthetic SEBS gel, because gel offers an advantage clay doesn’t: you can capture the deformation with high-speed video, measuring both the depth and diameter of the bulge frame by frame as it develops. This lets testers calculate acceleration and estimate the volume of displaced tissue, giving a more complete picture of the trauma risk than a static clay impression.
Forensic Investigation
In criminal cases, forensic examiners use gel blocks to reconstruct shootings. By firing the same type of ammunition recovered from a crime scene into calibrated gelatin, investigators can estimate wound depth, bullet trajectory, and fragmentation behavior. The wound profiles generated in gel don’t perfectly replicate injuries in a human body, which contains bone, organs, and varying tissue densities. But they provide a reasonable approximation that can be mapped onto the body to help explain injury patterns, estimate shooting distance, or compare the effects of different weapons involved in an incident.
The ability to recover intact or fragmented projectiles from the gel is also valuable. Examiners can study how a bullet deformed, whether its jacket separated, and where fragments ended up relative to the entry point. All of this helps reconstruct what happened during a shooting with more physical evidence than autopsy findings alone can provide.
Medical Training Simulators
Because ballistic gel mimics soft tissue and shows up well on ultrasound, medical educators have adapted it into training phantoms for procedures that are difficult to practice on real patients. One example: researchers built a low-cost, reusable shoulder model from ballistic gelatin that allowed trainees to practice ultrasound-guided joint injections. After a single 30-minute session with the phantom, participants reported significantly increased comfort performing the procedure. The gel’s acoustic properties make it behave like real tissue under an ultrasound probe, so trainees see realistic images while learning to guide a needle to the right spot.
These homemade phantoms cost a fraction of commercial simulation models, and because gelatin can be remelted and recast, a single batch can serve multiple training sessions. This has made ballistic gel an appealing material for emergency medicine and orthopedic training programs working with limited budgets.
Automotive and Military Impact Research
Beyond firearms, ballistic gel appears in any field that needs to understand what happens when an object strikes human tissue at speed. Automotive safety engineers use it to study how shrapnel or debris affects passengers during collisions. Military researchers test the lethality of explosive fragments, shrapnel, and less-lethal munitions like rubber bullets. The same principles apply in each case: fire or propel an object into a calibrated block, then measure how deep it goes and how much tissue disruption it would cause. The gel provides a humane, reproducible alternative to the animal carcasses and cadavers that were used for this research before standardized gelatin protocols existed.