Ballistic gelatin

Ballistic gelatinis a testing medium designed to simulate the effects of bullet wounds in animal muscle tissue. It was developed and improved byMartin Facklerand others in the field ofwound ballistics.It is calibrated to match pig muscle, which is ballistically similar to human muscle tissue.^[1]^[2]^[3]

Ballistic gelatin is traditionally asolutionofgelatinpowder in water. Ballistic gelatin closely simulates thedensityandviscosityof human and animalmuscletissue, and is used as a standardized medium for testing the terminal performance offirearms ammunition.While ballistic gelatin does not model the tensile strength of muscles or the structures of the body such as skin and bones, it works fairly well as an approximation of tissue and provides similar performance for most ballistics testing; however, its usefulness as a model for very low velocity projectiles can be limited. Ballistic gelatin is used rather than actual muscle tissue due to the ability to carefully control the properties of the gelatin, which allows consistent and reliable comparison ofterminal ballistics.

History

The FBI introduced its own testing protocol in December 1988 as a response to the1986 Miami shootout,and it quickly became popular among US law enforcement agencies.

Preparation

Gelatin formula

The most commonly used formula is an FBI-style 10% ballistic gelatin, which is prepared by dissolving one part 250bloomtype Agelatininto nine parts of warm water (by mass), mixing the water while pouring in the powdered gelatin. It is chilled to 4 °C (39 °F).^{[citation needed]}The olderNATOformula specifies a 20% solution, chilled to 10 °C (50 °F), but that solution costs more to prepare, as it uses twice the amount of the gelatin.

In either case, a 1988 research paper by Martin Fackler recommends that the water should not be heated above 40 °C (104 °F), as this can cause a significant change in the ballistic performance.^[4]However, this result does not seem to be reproduced in a later study.^[5]

Calibration

To ensure accurate results, immediately prior to use, the gelatin block is calibrated by firing a standard.177 caliber (4.5 mm)steelBB from anair gunover agun chronographinto the gelatin, and the depth of penetration measured. While the exact calibration methods vary slightly, the calibration method used by the United StatesImmigration and Naturalization Service's National Firearms Unit is fairly typical. It requires a velocity of 183 ± 3 m/s (600 ± 10 ft/s), and a BB penetration between 8.3 and 9.5 cm (3.3–3.7 in).^[6]

In his bookBullet Penetration,ballistics expert Duncan MacPherson describes a method that can be used to compensate for ballistic gelatin that gives a BB penetration that is off by several centimeters (up to two inches) in either direction. MacPherson's Figure 5-2, Velocity Variation Correction to Measured BB Penetration Depth, can be used to make corrections to BB penetration depth when measured BB velocity is within ±10 m/s of 180 m/s. This method can also be used to compensate for error within the allowed tolerance, andnormalizeresults of different tests, as it is standard practice to record the exact depth of the calibration BB's penetration.^[7]

Synthetic alternative

Ballistic gels made from natural gelatin are typically clear yellow-brown in color, and are generally not re-usable. The more expensive synthetic substitutes are engineered to simulate the ballistic properties of natural gelatin, whilst initially being colorless and clear. Some synthetic gels are also re-usable, since they can be melted and reformed without affecting the ballistic properties of the gels.^{[citation needed]}

Synthetic formula

Synthetic ballistic gels are typically made of an oil and a polymer instead of gelatin and water, most commonly used is white mineral oil and a styrene polymer blend, polymers used include:

styrene-butadiene-styrene polymers;
styrene isoprene-styrene polymers;
styrene-ethylene-butylene styrene polymers;
styrene-ethylenepropylene polymers;
styrene-ethylene butylene polymers;
styrene-butadiene polymers; and
styrene-isoprene polymers.

The gel usually includes about 12% to 22% by weight of the polymer, but it depends on what polymers is used.

Heating temperatures vary depending on what polymer and oil is used, but should never go over 275 °F (135 °C).

The polymer and oil solution is extremely sensitive to moisture - when moisture comes in contact with the solution, bubbles form when heat is applied.

Polymer should not be added to heated up oil like gelatin is to water; the polymer and oil should be mixed when no heat is present.

Dwell times are recommended after mixing the polymer and oil to prevent bubbles forming when heat is applied. These "dwell" times can go up to 12 hours if the air is above about 60 °F, or at the very least 24 hours if the air is at cooler temperatures.

These discoveries were made by Darryl D. Amick.^[8]

Uses

Since ballistic gelatin mimics the properties of muscle tissue reasonably well,^[9]it is the preferred medium (over real porcine cadavers) for comparing the terminal performance of different expanding ammunition, such ashollow-pointandsoft-point bullets.These bullets use thehydraulicpressure of the tissue or gelatin to expand in diameter, limiting penetration and increasing the tissue damage along their path. While theHague Conventionrestricts the use of such ammunition in warfare, it is commonly used by police and civilians indefensive weapons,as well as policesniperand hostage-rescue teams, where rapid disabling of the target and minimal risk of overpenetration are required to reducecollateral damage.

Bullets intended forhuntingare also commonly tested in ballistic gelatin. A bullet intended for use hunting smallvermin,such asprairie dogs,for example, needs to expand very quickly to have an effect before it exits the target, and must perform at higher velocities due to the use of lighterbulletsin thecartridges.The same fast-expanding bullet used for prairie dogs would be considered inhumane for use on medium game animals likewhitetail deer,where deeper penetration is needed to reach vital organs and assure a quick kill.

In television theMythBustersteam sometimes used ballistics gel to aid in busting myths, but not necessarily involving bullets, including theexploding implantsmyth, thedeadly card throw,and theceiling fan decapitation.They sometimes placed real bones (from humans or pigs) or synthetic bones in the gel to simulate bone breaks as well.

The UStelevisionprogramForged in Fireis also known to use ballistics gelatin, often creating entire human torsos and heads complete with simulated bones, blood, organs and intestines that are cast inside the gel. Various bladed weapons are then tested on the gel torso in order to simulate and record the destructive effects the weapons would have on a real human body.

References

^Fackler, Martin LEffects of small arms on the human body Archived2012-02-18 at theWayback Machine.Letterman Army Institute of Research, California.
^Massad Ayoob (May/June, 2005) Backwoods Home Magazine.Wound Ballistics, Ballistic Injury, Stopping Power, Gunshot Wounds.Firearmstactical.com. Retrieved on 2012-08-14.
^Choose your ammo... police style:"This resulted in the FBI Wound Ballistics Workshop of 1988 in Quantico, Virginia. Among those present were Dr. Martin Fackler, head of wound ballistics research for the US Army's medical training center, Letterman Institute. Fackler had developed an improved ballistic gelatin model that he had scientifically correlated to swine muscle tissue, which in turn is comparable to human muscle tissue. He hypothesized that wound depth was much more important than previously thought, and recommended ammunition that could send a bullet at least twelve inches into his ballistic gelatin."
^Fackler ML, Malinowski JA (1988). "Ordnance gelatin for ballistic studies. Detrimental effect of excess heat used in gelatin preparation".Am J Forensic Med Pathol.9(3): 218–19.doi:10.1097/00000433-198809000-00008.PMID 3177350.S2CID 12266221.
^Jussila J. (May 10, 2004). "Preparing ballistic gelatine—review and proposal for a standard method".Forensic Science International.141(2–3): 91–98.doi:10.1016/j.forsciint.2003.11.036.PMID 15062946.
^"INS National Firearms Unit Ballistic Gelatin Test Protocol".Firearms Tactical Institute.September 1, 1998. Archived fromthe originalon January 23, 2013.
^MacPherson, Duncan (1994).Bullet Penetration: Modeling the Dynamics and the Incapacitation Resulting from Wound Trauma.El Segundo, California: Ballistic Publications.ISBN 0-9643577-0-4.
^"Gel compositions as muscle tissue simulant and related articles and methods".
^Breeze, J.; Hunt, N.; Gibb, I.; James, G.; Hepper, A.; Clasper, J. (2013). "Experimental penetration of fragment simulating projectiles into porcine tissues compared with simulants".Journal of Forensic and Legal Medicine.20(4): 296–299.doi:10.1016/j.jflm.2012.12.007.ISSN 1752-928X.PMID 23622477.