The tissue simulant utilized in FBI ballistic tests is Vyse ordinance gelatin. The mixture is 10%, by weight. The mentioned research shows that properly calibrated 10% ordinance gelatin is a reliable tissue simulant. 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 (2.95" – 3.74"). During FBI tests, any gelatin blocks which fail the calibration test are discarded. Calibration results are not published due to the Pass/Fail nature of the test.
The gelatin is mixed in the following manner (assuming a 20 pound block is desired):
Weigh out two (2) lbs. of gelatin powder and place aside.
Weigh out 18 lbs. of hot 60° C (140° F) water in a plastic bucket. (Note: The FBI utilizes a scale which weighs to the nearest .01 lb).
Place 2.5 ml of Foam Eater in water.
Place approximately .5 ml. of oil of cinnamon into water (prevents 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 4 hours.
Write date on small square of cardboard and place on top of mixture.
Place pan with mixture into refrigerator set at 4° C (39.2° F).
Allow to cure for 36 hours (note: larger blocks require longer cure time e.g. an 80lb block requires 96 hours to cure).
Blocks, over time, deteriorate and are temperature sensitive. Former FBI publications advocated utilizing blocks within 20 minutes of removal from the refrigerator (a general statement pertaining to ambient temperature indoors). Allowable time outside the refrigerator is, however, relative to the temperature of the test environment (e.g. a block removed from a refrigerator and maintained in a room at the same temperature as the refrigerator will retain its calibration significantly longer than one placed outside on a hot summer day). Note: some authorities believe mixing procedures may vary the consistency of gelatin. FBI studies indicate, however, that a block which displays the required level of penetration, within the required velocity range, is a “valid” tissue simulant.
The FBI Ballistic Research Facility conducts its tests in an environmentally controlled shooting laboratory. Blocks of gelatin are removed from the refrigerator and checked for calibration. Only valid blocks are used for testing. Blocks used in testing of conventional pistol ammunition are approximately 6.25" X 6.25" X 16". The initial block of gelatin used in a test is called the Primary Block. Each Primary block is utilized for a maximum of 5 shots, one in each corner, approximately 1.75" from the nearest edge, and one in the center. Tests conducted by the FBI indicate this placement of shots results in substantially the same penetration as single shots into virgin blocks of gelatin. Any shots which cross the wound path of previous shots are refired. Primary blocks are not utilized for more than 5 shots, to include any shots which are refired.
The acceptable measure of a block of gelatin is a .177-caliber ground steel BB to penetrate 3.34 inches (8.5 cm) when launched at 590 fps.