Ballistic gelatin comparisons: Part III
There's a clear difference between synthetic and organic gelatin that law enforcement needs to understand
In Part I of this series, we talked a little bit about the history of ballistic testing since the 1970s, and how the FBI’s efforts after the 1986 Miami gunfight helped to create a national standard for testing law enforcement handgun ammunition. That standard, now referred to as the “FBI protocol,” established a clear and repeatable process for testing ammunition in 10% calibrated gelatin, and defined a set of parameters for law enforcement duty ammunition performance that rapidly became the profession’s yardstick.
It’s significant that the FBI protocol provided standardization where there was none before. Before the protocol was developed, each law enforcement agency and manufacturer drafted their own standards for ballistic testing and used a variety of test mediums in their evaluations. With the widespread adoption of the protocol and 10% calibrated gelatin as a test medium, law enforcement and industry now had a single, repeatable, comparable process for testing duty ammunition.
In Part II, we discussed how this industry standardization is potentially in jeopardy from a new and popular ballistic test medium, made of a clear synthetic. Small scale testing indicated that bullets fired into the clear synthetic product were performing differently than they did in the FBI-specified, 10% calibrated gelatin, making it inappropriate to measure their performance with the FBI yardstick.
As a result of this apparent discrepancy, plans were made to conduct a thorough test of the clear synthetic test medium to verify whether it gave comparable results to 10% calibrated gelatin. We discussed the details of the test plan in Part II, and now it’s time to discuss the results.
The bottom line, upfront
There were two significant findings from this test.
First, none of the factory fresh, clear synthetic blocks passed FBI calibration, despite the fact that the included warranty cards indicated they would. Each of the four new blocks had warranty cards that indicated that calibration BBs had penetrated 3.5 inches in sister samples from the same lot, but when we tested the blocks, we recorded BB penetrations ranging between 4.625” and 4.875”. Due to the elastic nature of the material, the BB would penetrate, then spring back to a final resting place that was short of the overall penetration depth (the same happens in organic gelatin). The FBI measures the overall penetration depth, but even the shorter resting distance of our calibration BBs ranged between 4.0” and 4.125” in the clear blocks, which is beyond the FBI’s acceptable maximum overall penetration of 3.74”.
Second, our test of six different 9mm cartridges from five different manufacturers indicated that bullets tend to under expand and over-penetrate in the clear synthetic gelatin, compared to 10% calibrated gelatin. There was an insignificant difference in retained weight between the two test mediums, with the bullets fired into the clear synthetic losing the smallest fraction of their weight.
These tendencies were the same for bare gelatin and gelatin covered with FBI-standard “heavy clothing.” They were the same for all tested variations of bullet weight, velocity and construction, as well.
By the numbers
To help quantify these differences, we’ll compare how a particular bullet design performed in both test mediums, in terms of penetration, expansion and retained weight. There will be no attempt to compare one cartridge to another since it was not our objective to compare ammo. Our task was solely to compare how the clear synthetic gelatin stacked up against 10% calibrated gelatin as a test medium, so each bullet will only be judged on how it performed against itself in the two test mediums, and values will be expressed as percentages, instead of raw numbers.
So, let’s start with expansion in the bare (uncovered) gelatin. In our test, the sampled bullets expanded less in the bare, clear synthetic gelatin than they did in the bare, 10% calibrated gelatin. The average expansion for all the bullets we tested in the clear synthetic was only 92.2% of what we saw for those same bullets in the 10% calibrated gelatin, with comparable expansion ranging from a low of 89.4% (the standard pressure, 124 grain Federal HST) to a high of 96.7% (the 147 grain Speer G2).
When we added the FBI heavy clothing layer in front of the two gelatin products, the same relationship held true – the bullets fired into the clear synthetic gelatin expanded less than they did in the organic, 10% calibrated gelatin, giving us only 89.3% of the expansion we saw in the calibrated gelatin, on average. In the heavy clothing test, the lowest clear synthetic expansion we saw was 84.4% of the calibrated gelatin value (the 147 grain Speer G2), and the highest was 92.3% (the standard pressure, 124 grain Federal HST).
Our testing indicates there is something different in the density and/or elasticity of these two types of gelatin that makes bullets expand differently in each of them. The bullets fired into the clear synthetic gelatin expanded around 8% (bare) to 11% (heavy clothing) less, on average, than they did in the organic, 10% calibrated gelatin.
With the decreased expansion, it’s no surprise that the bullets fired into the clear synthetic gelatin also penetrated further than they did in the organic, 10% calibrated gelatin. Because the smaller surface area of these projectiles created less drag in the clear synthetic than the organic gelatin, the bullets retained more of their energy and went further.
Looking first at the bare gelatin results, on average, the sampled bullets penetrated 35.5% deeper into the clear synthetic product than they did in the organic, 10% calibrated gelatin, with a range between 34.4% (the 135+P Hornady Critical Duty) and 36.3% (the standard pressure, 124 grain Federal HST).
When we added the FBI heavy clothing layer in front, the bullets fired into the clear synthetic continued to penetrate deeper than they did in the organic gelatin, by a startling average of 48.1% for all the tested cartridges. The highest difference in penetration was 56.1% more in the clear synthetic than the organic (the standard pressure, 124 grain Federal HST), and the lowest difference was 38.2% more in the clear synthetic than the organic (the 135+P Hornady Critical Duty).
The percentages are fine, but to put things into better perspective, the 48.1% average increase in penetration for the six loads fired into the clear synthetic gelatin, covered in heavy clothing, represents a little more than 6” of extra penetration in the clear synthetic product, compared to the organic product.
We had previously noted that the makeup and behavior of (nominal) 10% organic gelatin can vary slightly, due to differences in humidity, temperature and the source of the gelatin. As such, the FBI considers organic gelatin to meet calibration standards if a 0.177” BB fired at 590 +/-15 fps penetrates to a depth between 2.95-3.74 inches.
Readers will recall that our prior testing indicated this calibration range could account for as much as a 1.25” difference in penetration distance (typically, less than 1”, but we did have a 1.25” data point in our abbreviated, 3-round test) in the organic gelatin, so we allowed for a very conservative 1.5” difference between the clear synthetic gelatin and organic gelatin, to level the playing field.
Even with this 1.5” handicap applied, the bullets fired into the clear synthetic gelatin consistently penetrated farther than they did in the organic gelatin – on the order of about 24% (bare) to 36% (heavy clothing) more, on average.
The bullets fired into the clear synthetic and organic gelatin didn’t shed much, if any, of their weight, regardless of whether the gelatin was bare or covered with heavy clothing. However, there was an incredibly minor tendency for the clear synthetic bullets to lose the tiniest bit more weight than the organic gelatin bullets.
In bare gelatin, the bullets fired into the clear synthetic lost only 0.2% more weight, on average, than those fired into the organic gelatin (with a high-low range of 0.1% to 0.4%). When the gelatin was covered with heavy clothing, the bullets fired into the clear synthetic lost only 0.3% more weight, on average, than those fired into the organic medium (with a high-low range of 0.0% to 1.4%).
In the real world, these differences are insignificant and should not influence bullet performance. We’re only reporting them here to be thorough, but the takeaway for the reader should be that there is no meaningful difference in retained weight between the clear synthetic and organic, 10% calibrated gelatin products.
Taking stock of the test results
It’s important that the warranty cards that stated the clear synthetic gelatin blocks had passed FBI calibration standards were not accurate for the four samples we used in our testing. Our calibration BBs penetrated much further in the virgin blocks than the FBI standards allow, providing an early warning that the blocks would not give results comparable to 10% calibrated gelatin, prepared according to FBI specifications.
It’s interesting that even after the blocks had been melted down after the first use and reconstituted for a second round of testing (allowable, per the manufacturer), the material continued to fail FBI-standard calibration – although just barely. In our second round of calibration tests, the reconstituted blocks allowed BBs to penetrate between 3.75” and 3.825”, which is much closer to the FBI specification than the virgin blocks allowed, but still just beyond the far limit for penetration.
Given that these blocks failed FBI standards for calibration each time, it’s unsurprising that the bullets we fired into them penetrated more deeply than they did in 10% calibrated gelatin. However, the amount of that extra penetration was a little surprising. We were not prepared for bullets to penetrate an average of more than 6” deeper into the clear synthetic gelatin than the organic gelatin, in the heavy clothing test, for example.
With respect to the tested product, our results suggest the following implications:
- The clear synthetic gelatin must be calibrated by the user before use. The factory warranty cards cannot be relied upon to give an accurate measure of the product’s calibration.
- The clear synthetic gelatin currently demonstrates a tendency to limit bullet expansion and increase bullet penetration, compared to FBI-standard, 10% calibrated organic gelatin. Based on our limited sample, this tendency seems to apply irrespective of bullet manufacturer, materials, design, construction, weight, pressure, or velocity. It seems that bullets penetrate significantly more in the clear synthetic, even when acceptable variations in organic gelatin penetration depth are accounted for.
- The clear synthetic gelatin currently does not appear to be a suitable substitute for FBI-standard, 10% calibrated organic gelatin if the bullets will be measured and evaluated according to FBI performance standards. Because the bullets we tested behaved so differently in the clear synthetic gelatin versus the 10% calibrated organic gelatin, it’s not appropriate to use the FBI standards ‒ which were designed to be applied to 10% calibrated organic gelatin – to measure bullet performance in the clear synthetic product.
In example, it’s inappropriate to measure and evaluate bullet penetration according to the FBI protocol (which rewards bullets that penetrate between 12” and 18” in 10% calibrated gelatin and penalizes those that fall outside this window) when bullets may routinely penetrate an extra 6” in the clear synthetic. If we did apply FBI standards to the clear synthetic, we might “pass” a bullet that normally fails the FBI protocol because it doesn’t penetrate deeply enough. Conversely, we might “fail” a bullet because it over penetrates in the clear synthetic, even when it normally passes the FBI protocol because by remaining within FBI penetration limits.
- There is no apparent “conversion” between data derived from 10% organic gelatin and the current version of the clear synthetic. Unfortunately, our limited test doesn’t indicate a conversion “shortcut” is likely. It would be convenient if we could develop a conversion factor that would equate the organic gelatin and clear synthetic gelatin, but our data indicate that bullet performance is too variable in these mediums to develop a universal “rule of thumb.” Perhaps a skilled mathematician could derive a constant from a more complete sample, but we’re not seeing one lurking in the data.
The road ahead
This test was a cooperative effort between multiple parties interested in obtaining useful data on the performance of the new synthetic gelatin compared to organic gelatin. Information was freely shared among the parties, including the manufacturer of the clear synthetic product.
It’s important to note that the clear synthetic manufacturer was unhappy with how their product performed in our test, which has inspired them to take a close look at their product and quality control practices. As of press time, the manufacturer is engaged in an effort to modify the formula of the clear synthetic gelatin to enable it to pass FBI calibration. They are also taking steps to improve their quality control and inspection protocols to ensure that their products will comply with FBI standards for ballistic gelatin. When these changes are complete, a follow-on test will be conducted to evaluate the performance of the upgraded product, and the results will be published here.
For now, however, we’re not comfortable with having law enforcement officers and agencies make ammunition decisions, using FBI protocol criteria, based on the results of testing in the current version of the clear synthetic gelatin. As a result of this project, there may be a time in the near future when an improved formula makes the clear synthetic a suitable substitute for FBI calibrated gelatin, but we’re not currently there.
Enhancing the clear synthetic product would be an important advancement because we believe its advantages are numerous and compelling. If the formula for the clear synthetic could be altered to provide performance equivalent to that of 10% calibrated gelatin, it would be the runaway favorite for this kind of work. Legions of manufacturers, law enforcement agencies and individual hobbyists would cheer in unison to have a ready-made, temperature-stable clear gelatin that accurately replicated the troublesome organic gelatin. It would be a huge win for all of us to see that happen.
Until then, however, don’t throw away your mixing buckets and molds.