Ballistic gelatin comparisons: Part II
A variety of bullet weights, velocities, pressure levels, styles and designs were represented in the data, to ensure the broadest comparison of the two test mediums
In Part I of this series, we discussed how concerns of inconsistencies between the performance of handgun ammunition in FBI-standard ballistic gelatin and the new, clear synthetic gelatin that’s becoming increasingly popular, encouraged a comparison test of these two mediums.
Since there was mounting evidence that some law enforcement agencies were using results obtained from the new, synthetic product to make duty ammunition choices, it was important to verify whether those results could be evaluated according to FBI performance standards that were developed using 10%, calibrated organic gelatin.
Would the synthetic gelatin product perform close enough to the organic gelatin that the data obtained in the two mediums would be directly comparable in an “apples to apples” fashion, or would differences in the two test mediums turn things into an “apples to oranges” comparison?
To answer that question, I worked with Hornady Manufacturing Company representatives to design a comparison test of the two mediums.
Before we committed resources to a large-scale test, we began with a small-scale test that compared the performance of Hornady’s 9mm +P, 135 grain, Critical Duty Flexlock bullet in the two mediums. If this small test indicated there was a discrepancy, we would proceed with plans for a more exhaustive comparison.
In Hornady’s tests of its 9mm +P, 135 grain, Critical Duty Flexlock bullet, the projectile normally penetrated around 14.5 inches in bare, calibrated gelatin. Independent testing of this projectile by the US Department of Homeland Security (14 inches) and the FBI (14 inches), as well as joint Hornady/agency testing with the Mesa (Arizona) Police Department (14 inches), Nebraska State Patrol (14.75 inches) and the Texas Department of Public Safety (14.25 inches), validated this performance (using a variety of pistol makes and barrel lengths) and confirmed Hornady’s expectation for this projectile.
However, when Hornady tested the same ammunition in the clear, synthetic gelatin substitute (same test protocol and conditions, including barrel length and lack of an intermediate barrier) the 9mm FlexLock bullet penetrated around 19 inches. This represented a 31% increase in penetration in the clear synthetic product compared to FBI-calibrated gelatin.
Additionally, the profile of the wound tracks was different in the synthetic product in comparison to FBI-calibrated gelatin, with an almost nonexistent Maximum Temporary Cavity (MTC) dimension, and a longer Depth to Maximum Cavity (DMC), followed by an “ice pick” kind of penetration after that.
Based on these initial results, plans were made to proceed with a large-scale comparison test of the two products.
Large-scale test protocol
It was important to ensure that large-scale testing would be conducted in accordance with standard FBI protocols, with the highest measures of quality control and consistency, to develop a useful set of data for comparison.
This meant a professional facility would be required for testing. While there are many “backyard ballisticians” who prepare and shoot organic gelatin, such settings can introduce variables that will skew data. For instance, since organic gelatin is highly sensitive to temperature and can break down quickly in heat and direct sunlight, it must be carefully preserved at consistently low temperatures and shot for record before it warms. It’s difficult to maintain these temperatures when a block must be transported to an off-site test facility in a cooler, and shot in warm, ambient conditions – perhaps even in direct sunlight. It’s even more difficult to do this with multiple blocks and keep them all at a consistent temperature for reasonable comparison to each other. Spread the testing process out to multiple days, and the consistency challenge becomes even more complex.
The two-day test would be conducted at the same facility that Hornady uses for internal research and quality control testing, as well as testing for its extensive list of law enforcement, military and industry clients. This environmentally controlled facility would allow for consistent and measurable conditions and would allow access to calibrated equipment for measuring bullet velocities and weights. Organic gelatin blocks could be preserved at ideal and consistent temperatures in nearby industrial refrigeration units until they were removed for immediate testing, conducted only yards away.
All gelatin blocks – both organic and synthetic – would be tested for calibration in accordance with FBI standards, immediately prior to shooting. This test would involve firing a 0.177” steel BB into the gelatin at a measured velocity of 590 +/- 15 feet per second, and checking for penetration depth between 2.95 – 3.74 inches. Any organic gelatin block that failed to meet these calibration standards would be rejected to ensure the synthetic product was only compared to FBI-spec ballistic gelatin.
A single pistol (same serial number) would be used to conduct all testing for consistency. The Glock 17 was chosen as it is the most widely used 9mm service pistol in U.S. law enforcement. The test pistol was a Glock 17M model, as currently issued by the FBI.
In order to generate a data set that was not limited to Hornady products, the author solicited assistance from other major ammunition manufacturers to supply product samples. Law enforcement duty ammunition was received from both Speer and Federal in response to this request. Winchester and Remington were unable to supply samples, so the author purchased ammunition from these marques via commercial channels, to ensure they would be represented in the data.
A variety of bullet weights, velocities, pressure levels, styles and designs were represented in the data, to ensure the broadest comparison of the two test mediums. “Barrier blind” bullets from Hornady (Critical Duty 124+P and 135+P) and Speer (147 grain G2) were included, as well as advanced hollowpoint designs from Federal (124 grain HST) and Winchester (127+P+ Ranger SXT). A “low-tech” traditional jacketed hollowpoint from Remington (115+P HTP) was also tested to help broaden the selection.
The synthetic gelatin was sourced from a commercial vendor and the order was filled and shipped to Hornady by the manufacturer, who had been fully briefed that the blocks would be used in this testing.
The organic gelatin was prepared in accordance with FBI instructions. The blocks that were shot on the first day of testing were prepared in advance of the author’s arrival by Hornady personnel, and the author personally prepared the blocks which were used on the second day of testing.
Two individuals – one from Hornady and the author – would take all the measurements, and compare results with each other to identify errors and correct discrepancies before the final results were recorded.
An additional question
It’s important to understand that the FBI specifications for gelatin calibration constitute a range of acceptable penetration depths for the test BB projectile. This is because organic gelatin may demonstrate slight variations in density as a result of mixing ratios, environmental humidity and the source of the organic gelatin itself. Additionally, the density may change slightly as the core temperature of the gelatin varies between acceptable extremes.
The FBI has determined that organic gelatin will provide useful and comparable results as long as the 0.177” calibration BB penetrates to a depth between 2.95–3.74 inches. Anything on either side of this band is considered unacceptable for measuring bullet performance in accordance with FBI standards for penetration, expansion and retained weight.
In order to provide the fairest comparison for the synthetic gelatin, it was important to quantify the performance change between bullets that were fired into “minimum spec” FBI gelatin and “maximum spec” FBI gelatin. This would allow us to compare the synthetic results to the full range of acceptable measures from organic gelatin, mixed in accordance with FBI standards.
To determine this difference, the ratio of organic gelatin powder to water was slightly altered to create gelatin blocks that would calibrate at both the high and the low ends of BB calibration. The “minimum spec” block we prepared calibrated at 3.00” and the “maximum spec” block calibrated at 3.625” when tested with the 0.177” BB, which was about as close as you could get to the FBI goalposts.
Three rounds each of Hornady 124+P and 135+P Critical Duty were fired into the minimum and maximum blocks, then measured. Retained weight was 100% in both blocks for all 12 rounds, and there was negligible difference in expanded diameter between them (an average of 0.005” more expansion – less than a 1% difference – for rounds fired into the minimum block). However, the penetration distance changed about 1.25” for the 135+P and about 0.42” for the 124+P between the minimum and maximum block. These distances were slightly longer than those noted in previous testing conducted by Hornady, using industry-standard 5 round samples (in lieu of our abbreviated 3 round samples), which revealed a 1.00” maximum (typically, less than 1.00”) difference between gelatin that calibrated at the minimum and maximum FBI specs.
From this, we conservatively concluded that any variation in penetration of less than 1.5” (including a generous 0.25” buffer over the already high 1.25” maximum average penetration observed in our 3-round test) in the synthetic gelatin could be ignored as statistically insignificant. Restated, if bullets penetrated 1.5” more in the synthetic gelatin than in the calibrated organic gelatin, we would judge the synthetic results as comparable to the organic medium.
Armed with this knowledge, and with a protocol that maximized consistency and repeatability, we began to shoot synthetic and organic gelatin with the selected ammunition.
Ambient temperature on the indoor range was 70-72 degrees, and organic gelatin blocks were kept at 38 degrees in a commercial refrigerator until they were taken out for calibration and testing, which occurred within minutes of removing them from the refrigerator. The synthetic gelatin blocks were stored on the range overnight and were kept at the 70-72 degrees ambient temperature of the range.
The organic and synthetic blocks were shot with 3 rounds each of the 6 models of ammunition (2 from Hornady, and 1 each from Speer, Federal, Winchester and Remington). In accordance with the FBI protocol, the blocks were shot at a distance of 10 feet from the muzzle of the Glock 17M pistol to the front face of the gelatin.
Each test medium was shot in accordance with Tests One and Two of the FBI protocol. In Test One, bullets are fired into bare gelatin, and in Test Two, the gelatin blocks are covered with FBI-standard “heavy clothing,” which consists of four layers of material, to include:
- One layer of cotton t-shirt material (approximately 5.25 ounces per yard, 48 threads per inch);
- One layer of cotton shirt material (approximately 3.5 ounces per yard, 80 threads per inch);
- One layer of Malden Mills Polartec 200 fleece, and;
- One layer of cotton denim (approximately 14.4 ounces per yard, 50 threads per inch).
The results and implications of this test will be discussed in the final segment of this series.