A colleague posed a question: Which is likely to penetrate more, a 9mm full metal jacket bullet fired from a pistol or a 5.56 fired from an AR-15 pistol? Hmmm. . . I had never really thought about it. To find out, I conducted gel penetration tests for both calibers fired into calibrated 10% Clear Ballistics gelatin blocks.
Ballistic gelatin is a testing medium designed to simulate the effects of bullet wounds in animal muscle tissue. Dr Martin Fackler (founder and head of the Letterman Army Institute of Research Wound Ballistics Laboratory) developed an improved ballistic gelatin model that he had scientifically correlated to porcine muscle tissue, which in turn is comparable to human muscle tissue.
The Federal Bureau of Investigation (FBI) adopted the Army ballistic gelatin model using 10%, (by weight) ordnance gelatin to use as a tissue simulant. The FBI fires a .177 inch steel BB at 590 feet per second (fps) with a 15-fps allowable variance to calibrate their ballistic gelatin. The BB must penetrate 2.9 inches - 3.74 inches. The gelatin must be stored at 40° F until just prior to testing which makes its use on outdoor ranges problematic. The FBI does its testing with the gelatin placed ten feet from the muzzle of the test weapon. For more information see the footnote below.*
For my testing I used Clear Ballistics brand blocks because they are reusable and are not sensitive to temperature changes. I used a Glock 19 for the 9mm and a generic AR-15 pistol with a 10.5-inch barrel (typical AR pistol barrel length) for the 5.56.
I tested the following ammunition:
-- Lake City 5.56 with the standard 55 grain full metal jacket bullet (FMJ)
-- Monarch 9mm with a 115 grain full metal jacket bullet
-- Winchester 9mm 115 grain full metal jacket bullet.
I fired five rounds of each brand from ten feet into bare gelatin. I placed two sixteen-inch blocks end to end because the 9mm FMJ bullet is known for its ability to penetrate.
Every Lake City 5.56 bullet broke apart and generally stopped within twelve inches in the first gelatin block. The Lake City 5.56 bullets were so fractured that it was not possible to recover all the pieces and link them to a particular bullet with one exception. I was able to recover fragments of one bullets that had fractured at the cannelure and it weighed eighteen grains--it had lost 67% of its weight. It appeared that all the fragments from all five bullets were still present in the ballistics gel (in various sizes ranging from almost microscopic to slivers of lead and bullet jacket) with one exception -- a small fragment exited the block at sixteen inches (see circle). The permanent cavities for the 5.56 rounds were two-three inches in diameter and approximately six-seven inches long. The dark areas in the picture represented lead "snow" resulting from bullet fragmentation.**
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| 5.56 rounds |
The Monarch 9mm 115 grain rounds penetrated the first block (sixteen inches) and an average of nine inches into the second block for a total penetration of twenty-five inches. The Winchester 9mm 115 grain rounds penetrated the first block (sixteen inches) and an average of eleven inches into the second block for a total penetration of twenty-seven inches. As expected, all recovered 9mm bullets retained 100% of their initial weight.
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| 9mm Rounds |
So, what does this testing tell us? First, do not use 9mm ball ammunition for self-defense unless that is all you have available. There is a plethora of hollow point 9mm ammunition from reputable manufacturers that will do the job better.
The testing also begs the question of 5.56 ammunition over penetration concerns in a home defense role—at least for the 5.56 military ammunition. Since I did not do a barrier test in this process, I am unable to comment on what this round would do after passing through a barrier. I suspect that its penetration after passing through barriers found in a typical house’s construction would not be a great concern.
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