Hi Guys! sorry for the delay in posting new material, training classes and the holidays got in the way. Here is an article that I found on another site from Red Dot Training Range in PA. Not sure who authored the piece, but it is dead on accurate. Due to the length, I will break it into two posts.
Ballistic gelatin has been used for decades as a consistent tissue simulant for testing how bullets behave upon impact. After the 1986 FBI Miami shootout, the FBI sought a more scientific, standardized way to test ammunition performance.
In 1988, the FBI’s Firearms Training Unit developed a rigorous ammunition testing protocol based on consultation with wound ballistics and medical experts. This protocol introduced 10% calibrated ballistic gelatin (10% gelatin by weight in water, kept at ~4 °C) as the standard test medium. Before this, there was no uniform standard. Agencies and ammo makers used everything from clay to wet phone books. The FBI’s adoption of calibrated gel provided a single, repeatable yardstick for comparing bullet performance.
What does “calibrated” mean? It means each gel block is tested with a standard projectile to ensure consistency. The FBI uses a 0.177″ steel BB fired at 590 ft/s (±15 ft/s); to pass calibration, the BB must penetrate 8.5 cm (about 3.35″) in the gelatin (acceptable range ~7.5-9.5 cm, or 2.95-3.74″). If the gelatin block is too soft or too dense (BB goes too deep or too shallow), it’s discarded. This calibration step ensures the gel’s density and resistance closely match the intended standard, roughly equivalent to the density of human muscle tissue. Research by the FBI and others found that properly calibrated 10% ordnance gelatin has mechanical properties similar to living muscle and can serve as a reliable surrogate for soft tissue in controlled tests.
Ballistic Gelatin in Standardized Testing (FBI Protocol)
The intended purpose of using calibrated gelatin is to provide a uniform medium to measure bullet penetration, expansion, and performance in a repeatable way. The FBI’s test protocol involves firing bullets into gelatin under a variety of scenarios to simulate real-world conditions. Each round is first shot into bare gelatin (a plain 10% gel block) at 10 feet, and then through several common barriers into gelatin.
The FBI protocol includes tests with heavy clothing, drywall (wallboard), sheet steel (auto body), plywood, and laminated auto glass in front of the gel. After passing through the barrier, the bullet enters the gelatin, and investigators measure how far it penetrated, how much it expanded, and how much weight it retained. This comprehensive test series became known as the “FBI protocol,” and it gave law enforcement a measurable standard for duty ammunition performance.
Ammunition that could penetrate 12-18 inches in 10% gel, while expanding and retaining weight, was deemed effective; less than 12″ penetration was considered inadequate (risking failure to reach vital organs), while over 18″ raised concerns of over-penetration.
In fact, 14-16″ of penetration is often cited as ideal. These numbers didn’t come out of thin air, they were informed by events like the Miami incident, where a bullet stopped short of an assailant’s heart.
The FBI’s research determined that ~12″ minimum penetration in gel was needed to ensure a bullet can reach vital organs even through an arm or from various angles. Bullets that fall short of 12″ in the standardized gel test are heavily penalized in scoring, reflecting that they might fail to incapacitate a threat in real life.
By establishing this protocol and the gelatin test medium, the FBI enabled apples-to-apples comparisons of ammunition. Gelatin testing today is used not only by law enforcement, but also by ammunition manufacturers and independent testers to evaluate personal defense ammo. The widespread adoption of 10% calibrated gel means that whether it’s a 9mm or a .45 ACP, one can directly compare their penetration depths and expansion under identical conditions.
This standardization has driven huge improvements in bullet design over the years. Bullet makers design jacketed hollow points specifically to perform well in the FBI gel tests, which correlates with better real-world performance. For example, after the FBI began these tests, many manufacturers improved their 9mm and .38 Special bullets (which had been considered under-powered) to penetrate deeper.
Modern 9mm defensive rounds, thanks to advanced bullet engineering (bonded cores, better expansion mechanisms, etc.), can now consistently meet the 12-18 inch penetration goal, just like larger calibers. In fact, the improvement has been so dramatic that the FBI, which shifted to .40 S&W in the 1990s for more penetration, eventually moved back to 9mm in the 2010s, once 9mm ammunition technology proved it could perform on par with the larger calibers in the gel tests.
What Ballistic Gelatin Represents (and What It Doesn’t)
It’s important to understand what ballistic gelatin is and is not. The 10% gelatin block is essentially a proxy for average density muscle tissue. When prepared and calibrated correctly, its density and resistance to penetration mimic muscle tissue reasonably well.
The FBI chose muscle as the benchmark because muscle is tougher than many other soft tissues (like fat) and is found throughout the body, making it a “worst-case” soft tissue scenario to test against.
In other words, if a bullet can penetrate 12-18″ of gelatin, it should penetrate deeply enough in a human aggressor even if it encounters cartilage, gristle, or has to go through an outstretched arm first. Ballistic gelatin is a homogeneous medium, the same consistency all the way through, which makes it excellent for repeatable tests.
Every calibrated gel block, whether in one lab or another, should perform alike, so results can be compared across different tests and sources. This uniformity is the strength of ballistic gelatin as a testing tool.
However, gelatin is not a perfect simulacrum of a human body. Real tissue are heterogeneous and complex: skin, fat, muscle, organs, and bones are layered and have different elasticity.
Human muscle and organs can shift, stretch, or tear in ways that a plain gel block might not capture. Gel blocks also lack bones. A bullet that sails 15″ through gel might break apart or stop early if it hits a femur or rib in a real target.
Moreover, gelatin typically shows an exaggerated temporary cavity on high-speed cameras, that dramatic ballooning blast effect you see in slow-motion gel videos.
In gel, you might observe a wide sphere of jello being pushed outward (a visual representation of the bullet’s shock wave and temporary cavity). In living tissue, much of that stretch may not translate to catastrophic damage. Muscle and organs are elastic to a degree and contained in the body; they don’t fling apart as dramatically. Many viewers see those slow-motion gelatin shots and imagine a person would be equally “blown apart,” but that’s a misunderstanding. In reality, handgun bullets, especially, do not usually produce extreme explosive trauma, the effects are often far less spectacular than gelatin videos suggest. In fact, experts often caution that gelatin test results allow educated guesses about performance in flesh, but they are not guarantees.
For instance, a bullet that expands to double its diameter and penetrates 14″ in gel is likely to cause a significant wound in a human, but exactly how it damages tissue (or whether it hits something vital) will vary case by case. Gel testing provides consistent baseline data, not a movie-style prediction of what will happen.
To address a specific misconception: “12 inches of gel penetration equals 12 inches of real-world penetration.” This is not a one-to-one equivalence. The 12″ (30 cm) measure in 10% gelatin is a standardized gauge under specific conditions. In a human body, a bullet’s path and depth will depend on what it encounters, penetrating 12″ of pure muscle vs. 12″ that include bone or tougher organs can be very different.
The FBI’s 12-18″ rule means that in a uniform medium analogous to muscle, the bullet can reach critical internal depths. It doesn’t mean an assailant’s body is 12″ thick or that a bullet will always travel exactly 12″ inside a person. Rather, if a bullet does 12″ in calibrated gel, we infer it should be capable of reaching vital organs from various angles (like a frontal shot that must pass through an arm first, or a side shot through layers of muscle).
Penetration in gel is best used comparatively, not literally. Think of gel results as a way to compare one bullet to another under the same conditions. If Bullet A penetrates 14″ and Bullet B 8″ in gel, we know A penetrates deeper in a consistent medium. But in a real encounter, if Bullet B hits no bones and Bullet A hits a rib, their actual penetration in the body might differ. The gel test simply sets an expectation that Bullet B might risk not penetrating enough under tougher conditions, whereas Bullet A has a larger safety margin. The key is that gel provides a controlled environment to measure bullet performance characteristics (penetration depth, expansion size, fragmentation, etc.) in a repeatable way.
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