Research shows that properly calibrated ordnance gelatin is a highly reliable tissue simulant. The tissue simulant used in FBI ballistic tests is called Vyse ordnance gelatin. It’s a mixture of 10 percent gelatin, by weight.
Vyse ordnance gelatin is mixed in 20-pound blocks using the following recipe:
Weigh out two (2) pounds of gelatin powder and place aside.
Weigh out 18 pounds of hot 60ºC (140ºF) water in a plastic bucket. (Note: The FBI utilizes a scale which weighs to the nearest .01 pound). Place 2.5 ml of Foam Eater in water. Add approximately 0.5 milliliters of oil of cinnamon into the water to prevent fungus growth.
While utilizing a battery-operated drill with a mixing paddle attached, mix the water to the point of forming a whirlpool but without introducing air into the mixture. While the water is being mixed, slowly add the gelatin powder.
Pour the mixture into a clean mold pan.
Allow to stand at room temperature for approximately four hours.
Write date on a small square of cardboard and place on top of mixture.
Place pan with mixture into refrigerator set at 4ºC (39.2ºF) and allow it to cure for 36 hours. Larger blocks require longer cure time.
The gelatin blocks are temperature sensitive and over time will deteriorate. So they should be used within 20 minutes of removal from the refrigerator. Allowable time outside the refrigerator is relative to the temperature of the test environment.
Testing done by the FBI Ballistic Research Facility is conducted in an environmentally controlled shooting laboratory. The blocks of gelatin are removed from the refrigerator and checked for calibration. Calibration of ballistic gelatin is verified by firing a .177 steel BB at 590 feet per second (fps), plus or minus 15 fps, into the gelatin, resulting in 8.5 centimeters (cm), plus or minus 1 cm, penetration. During the FBI tests, any gelatin blocks failing the calibration test are discarded.
Conventional pistol ammunition tests are conducted on blocks approximately 6.25x 6.25x16 inches in size. The initial block of gelatin used in a test is called the “primary block.” The primary block is used for a maximum of five shots, one in each corner, approximately 1.75 inches from the nearest edge, and one in the center. Any shots that cross the wound path of a previous shot are fired again.
