Without a helmet: a ballistics study showcases head injuries

Without a helmet: a ballistics study showcases head injuries

August 08, 2018


How head injuries can differ depending on the ammunition used


You get it- ballistic helmets are essential gear. You knew they were for soldiers, but you read our blog religiously and now you know why police officers, firefighters, and paramedics are using them as well. We spend a lot of time explaining that if you are in a profession that puts you at risk of being shot, a tested helmet can help protect you from a devastating or fatal head injury. Recently, we came across a study published in Military Medicine that illustrates in the clearest terms what happens when a human gets shot in the head. Well, not exactly the clearest terms- it’s a scholarly article written by and for doctors, so there is a fair amount of technical jargon inside. Fortunately for our non-doctor customers, we’re here to explain it in plain English.

What did these researchers study?

They researched the ballistic effects of five different types of handgun ammunition. As you probably know well, different types of ammunition are designed for different scenarios. In this study they fired five types of rounds: round hollow, partial metal-jacketed, full metal-jacketed, hollow-point, and Action 4. First, let’s go over how these rounds differ.

Full metal-jacketed rounds have lead cores covered in a coating, or “jacket”, of copper. The jacket is designed so that the bullet will maintain its shape, rather than deforming or fragmenting. In practice it has a higher velocity than other rounds, and thus is more likely to go through a target. By international agreement, these are the rounds most commonly used in regular militaries.

Partial metal-jacketed rounds also have lead cores covered in a jacket of copper, except for the tip of the bullet which is uncovered lead. The exposed lead is soft, so that the bullet will expand and fragment when it hits the target. “Partial metal-jacketed projectiles thus impart a large amount of their kinetic energy to the target.” Translation: they have serious stopping power.

Hollow-point rounds are a kind of partial metal-jacketed round that has a small indent (or cavity) in the tip of the bullet, designed to fragment and transfer a lot of that kinetic energy we were just talking about. The study specifically used Hydra-Shok hollow-points, a proprietary round designed to emphasize “penetration and upset.” Translation: they go deeper and they predictably expand into a mushroom shape.

Action 4 rounds are a kind of hollow-point round with a plastic tip. Like the Hydra-Shok they are designed to mushroom, but the Action 4 is specifically designed to expand to a very wide diameter, for less penetration and greater stopping power.

Round hollow rounds are soft-cored with a copper jacket, and are designed to fragment upon impact.

Thanks for the refresher. How did they test the effects of the rounds?

They took x-rays and CT scans of severed pig heads, shot them, took a second set of x-rays and CT scans, and compared the images.

This study is just doctors shooting pigs in the face?

No, the doctors shot them “through the submental region in the occipital direction.” Translation: under the chin, toward the brain.


Basically it was as close as they could get to shooting a person in the head, while not shooting a person in the head. They do note that pig skin is less elastic than human skin, so exit wounds in humans may be larger.

Some researchers have used a ballistic gel to test the effects of bullets, but gels have uniform consistency while heads have soft and hard tissue together in the same space- skin, bones, cartilage, et cetera. The researchers expected to see different ballistic results with the head then they would with the gel, results that would be more useful to doctors treating head wounds. For example, the gel can't show you what happens when a bullet hits bone. (On our end, we did find some really cool videos of people firing into ballistic gel- check this one out below)

Video Credit: Tactical Rifleman YouTube Channel, published December 1 2017 

To ensure comparable results, every round used was 124 grains with a velocity of 235 meters per second. In addition, each was fired with the same 9mm Browning FN pistol.

Photo credit: von Seen et al.

What did they find out?

Each of the rounds had different ballistic effects when fired into the pig head. As you might have expected, the full metal-jacketed bullets went clean through the head, but the round hollow did as well. The others each tore apart soft tissue and fragmented bone, but lodged in the head without exiting, which is consistent with what we know from ballistics science. They also increased the volume of the tissue in the head due to the kinetic energy transferred. Translation: when the bullet stopped in the head, the energy that was causing it to move was taken on by the tissue surrounding it, which stretched it in the direction the bullet had been traveling.

Photo credit: von Seen et al.

The researchers emphasize that the damage each bullet caused was different from that of the others, and that without the x-rays and CT scans it would be difficult for doctors in the field to quickly determine what kind of projectile had been shot and what the exact damage would be. The below graph shows the different wound paths of the bullets in six figures side by side. The entry point for each bullet can be seen in the bottom middle of each figure, at roughly the point where the large white arrow tip points in Figure 2A. The wound path then traces up and to the right. In Fig. 2A-2D, you can see the bullets lodged in the upper right corner of each image; they appear white in the scan.

Photo credit: von Seen et al.

Comparing the CT scans in the graph makes it clear to the eye the varying effects of different kinds of ammunition. Even in a controlled environment, slight variations in the type of ammunition have dramatically variable damaging effects, so you can only imagine what kind of head injury you could sustain in an active shooter situation. 

We've talked before about how there is no such thing as a truly bulletproof helmet, but our helmets offer significant protection against what the enemy will throw at you. Generally speaking, full metal-jacketed rounds are more likely to penetrate helmets and body armor than the various partial metal-jacketed rounds, for the same reason previously mentioned- they transfer less kinetic energy to their target, so it takes more resistance to stop them. Click here to read the detailed results of lab tests we subjected our ATE helmet to, including ballistics penetration tests. 

This is why we take our mission of providing you high-quality, tested combat helmets so seriously. The best thing to do is prevent this kind of damage by purchasing high-quality protective gear. If you’re a soldier, police officer or anyone at risk of head injuries, you should consider buying a tactical helmet like the ATE.



MAJ Constantin von See; CPT Alexander Stuehmer; Nils-Claudius Gellrich, MD, DDS; Katrin S. Blum, MD; Kai-Hendrik Bormann, DDS; Martin Rücker, MD, DDS. “Wound Ballistics of Injuries Caused by Handguns.” MILITARY MEDICINE, Vol. 174, pp. 757-761, July 2009.

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