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terminal ballistics

Most Of What You Need To Know About Terminal Ballistics

The study of terminal ballistics is basically what happens when a bullet smashes into a target. That target may be fleshy, it may be solid. In any event, it's knowing what happens to your bullet and to the thing that it hits when it hits it.

Why does this matter? Well, if you're going to have ammunition that's intended on doing something other than just put a hole in paper, you should probably know a bit about what it does. Since we here are concerned with concealed carry, then that means understanding CCW ammo, design features, calibers and so on.

We won't go full physics lesson here; instead we'll cover the basics and how they apply to the average person and what they need to know. With that said…

Ballistic Gel Tests Vs The Real World


The first thing you need to know is that ballistic gel tests, while fun, are not a perfect simulacrum of what happens to a human (or other) body when struck by a particular bullet. It is instead an approximation from which you can infer the relative potential performance of ammunition.

So, to build on that a bit. The human body is made of a number of materials and tissues. Each is different and has different properties, such as the relative density and hardness of that material. Flesh is not very hard. Organs are a little harder, but not by very much. Bone is harder than wood.

Ballistic gelatin is made to simulate all of those tissues...but also none. Ballistic gel is made to the average density of all human tissues - flesh, blood, bone, hair, organ meat, etc. - to create a single material for the purposes of testing.

In other words, ballistic gel tells what a bullet does over an average of human tissues. It's not perfect. It's more like that ballistic gel kind of gives you ballpark.

Solid and fully jacketed bullets poke a hole through gel. Expanding bullets will (hopefully!) expand in the gel and come to a stop.

If you then add a barrier in front of it and/or layers of clothing, that gives you an idea of what you can expect in real world conditions, which is why the FBI testing protocol uses both. Again, you have to take it with a grain of salt, but it gives you a repeatable ballpark approximation.

Wounding Potential


One of the aspects that people look for in terms of ammunition performance and terminal ballistics wounding potential. It is the relative ability of a bullet to do damage to tissues, bone and so on.

It is also one of the most overrated and mythologized aspects of ballistics.

Wounding potential broadly correlates to caliber, in that the bigger the bullet the greater the wounding potential is. For instance, .45 ACP has more wounding potential than 9mm, which is part of the .45 ACP vs 9mm argument, for the sheer fact that a bullet .452 inches in diameter will hit more stuff than a bullet that's .355 inches in diameter.

Likewise, a .429-inch diameter bullet that's going very, very fast (ie a .44 Magnum) will do more potential damage than a .401-inch bullet that's moving at more moderate velocities.

Now, what people like to start saying or believing at this point is that "a bigger bullet lets in more air, and therefore lets out more blood." In theory? Sure! In reality? Not so much.

Here is where lab science butts up against physical reality.

So, wounding potential is true on paper. What ballistic gel doesn't do a good job of demonstrating is tissue elasticity. Human flesh, you see, stretches and wobbles; it's mostly fluid rather than solid. What happens when a bullet strikes tissue is it creates a temporary cavity much larger than the bullet itself, but the tissue contracts save for the actual hole that the bullet creates, which is the permanent wound cavity.

Permanent wound cavities are basically the size of the projectile. So while a 10mm or .45 ACP jacketed hollow point may have much greater wounding potential (just under 20 percent more) than 9mm, does it make much difference in the real world?

Maybe it did at one point, shooting 9mm or .38 S&W hardball...but not today.

Terminal Ballistics: Penetration, Expansion And Balancing The Two


Two aspects of terminal ballistics that people are highly concerned with are penetration (how deep the bullet goes) and expansion, or how big the bullet gets inside the target. Granted, many types of ammunition are non-expanding; full metal jacketed bullets and wadcutters don't really expand much, though they may get deformed.

Here, we will be talking about expanding ammunition. Since we here are - again - concerned more with what the armed civilian is more likely to use, we will mostly stay in that wheelhouse.

So, we understand WHAT expansion is. When a jacketed lead projectile (or totally lead) projectile enters a body, it's subjected to hydraulic pressure on the front of the projectile. This causes lead to flatten. In jacketed ammunition, the lead core peels back around the core leading to the mushroom shape that we're all familiar with.

So, which is better?

Neither is necessarily best on its own. Too much penetration and the round goes through the target, potentially wounding someone behind an attacker. Too little and it lodges in the surface without doing incapacitating damage.

The same is true of expansion. Too little and the bullet goes through the target. Too much and it fragments in the surface, too shallow to do its job.

Therefore, expanding ammunition must do a sufficient amount of both.

These attributes are determined by metallurgy and design. A conical-shaped projectile will penetrate deeper than a solid cylinder, such as a wadcutter. The more lead is exposed at the tip of a hollow point, the greater the projectile will expand and so on.

Ammunition makers tinker with bullet design to get a bit more of one than the other, or to hopefully arrive at a good balance of both.

The trend with modern expanding handgun ammunition - such as the typical 9mm ammo you might buy - is to favor expansion a bit more than penetration. This has been the trend for some time.

Stalwart designs such as Speer Gold Dot and Federal HST are known for impressive expansion and adequate penetration, and others - such as Hornady XTP or Winchester Silvertip - are known for not the best of expansion but plenty of penetration. Some, such as Federal Hydra Shok Deep, Hornady Critical Defense, Remington Golden Saber and the Winchester PDX/Ranger/former Black Talon family, are known to do both well.

Controlled expansion rounds are more the province of hunting ammunition. Cast solids and soft point rifle rounds, jacketed soft point magnum revolver rounds and so on are longer on penetration but do expand (after all, Remington Core-Lokt is called the "deadliest mushroom in the woods") just as jacketed hollow points do.

Additionally, another thing to know about what you see in ballistic gelatin and how it correlates to real-world performance is that you can expect less penetration but still expect expansion. There are too many variables to give a concrete ratio, but you could expect something like a ratio of 2:3 or in that ballpark. If a bullet penetrates 18 inches in gelatin, it will probably penetrate 12 inches in tissue.

Terminal Ballistics And "Stopping Power"

stopping power

A concept that gets brought up is that of "stopping power." Basically? It doesn't really exist...except that it kind of does.

This is where things get a bit complicated. For one, we all know that Newton's Third Law dictates that every action has an equal and opposite reaction. For a bullet to completely stop a person cold, it has to basically have the same incapacitating effect on the person shooting it.

The FBI found in ammunition tests that any bullet doesn't really have the capacity to instantly incapacitate a person until it reaches a velocity at least 2,000 feet per second UNLESS it is properly placed. Therefore, handgun rounds don't really have "stopping power."

However, it should be brought up that there is a loose correlation between what you might call "stopping power" or the ability to do incapacitating damage with the fewest possible rounds and the sheer size and weight of the projectile itself. In short, the bigger the bullet the greater the potential it has to do that.

A shotgun loaded with buckshot or a solid lead slug puts more than 400 grains of lead downrange. An AR-15 sends a 55- to 62-grain projectile. A .458 Remington Magnum can be used with grain weights between 325 grains and 500 grains. Shotguns are known man-stoppers. Dangerous game rifles, such as those chambered for .458 Remington Magnum, are known stoppers of very large animals such as Cape buffalo, rhinoceros and elephant.

Granted, this comes with a corollary.

Sheer projectile weight or bullet size does not get you anything if it isn't placed where it needs to go. While it's true that a bigger bullet can do more damage, it has to be put where it will actually do that damage. Shooting a charging bull elephant in the foot won't do a thing. Neither will shooting a determined attacker in the stomach, or at least won't right away.

Instead, the chest cavity, the spine or the mid skull (where the really sensitive bits are) must be targeted and the shot successfully placed to do serious damage. This is why many people favor heavy-for-caliber loads, such as 147-grain 9mm or .40 S&W loads of 180 grains, and .45 ACP in 230 grains as they carry a bit more momentum.

Read police shooting reports, and you'll find instance after instance of determined attackers being shot multiple times in critical areas and still fighting on, with head shots being required to end the fight.

Broadly speaking, what's been confirmed after years and years of testing and also real-world results is that 9x19mm and .38 Special are sort of the baseline in terms of reliable performance. Granted, there are some smaller rounds that do work (.380 Auto is known to work just enough to work if the shooter does their job, but not as well as 9mm) but the .38 Special and 9mm are more or less the floor in efficacy. Big enough to do what you need them to, but small enough for people to shoot them easily.

So, it's actually more the case to say that a bigger bullet has more potential to do incapacitating damage IF it's placed correctly AND if the individual (animal or person) you put it into decides they've had enough if they aren't killed instantly.

In other words, you don't really gain anything by going up to .45 ACP or 10mm except a bit more wallop on the backend, which will only matter if you are exceptionally accurate. The corollary to that is that a well-placed 9mm bullet of good construction will do broadly the same job.

Frangible And Fragmenting Rounds

fragmenting bullets

A more recent development has been the advent of frangible and fragmenting rounds. While these two bullet designs are related, they aren't the same.

The difference between frangible vs fragmenting is that frangible bullets shatter upon impact. Fragmenting rounds merely turn into shards, sort of like RIP rounds.

Frangible rounds are ideal for situations where overpenetration is a concern or in indoor locations. They are effective for self-defense at close range, so they are an appropriate choice in the home and elsewhere. Fragmenting rounds are as well.

However, there is a price, namely in penetration and expansion. Expansion is dramatic for both, but the expansion is a number of smaller pieces. This may not do incapacitating or fatal damage and exactly WHERE those fragments go is not predictable. Since the fragments are smaller, they travel to much shallower depths than an expanding hollow point will.

So...What Does Terminal Ballistics Tell Us About Self-Defense Ammo?


Mostly what we can learn about terminal ballistics is that we basically know what works. A quality hollow point that is accurately fired is the most proven effective round for self-protection, whether for the civilian carrying a concealed pistol, a home defense gun, or for the uniformed officer.

Decades of reports have shown that you can only depend on two things to stop an enemy. They are convinced psychologically to discontinue their behavior, or they are instantly stopped by compromising the musculoskeletal system or catastrophic trauma to the nervous system. Blood loss and cardiovascular trauma take too long to be effective in most cases of defensive shootings.

Bullets for purposes other than target shooting are tools. You, the person carrying the gun, are the person who must use it correctly.

What this means, more or less, is that you start with an appropriate bullet design in an appropriate caliber. In so doing, you use a bullet that will do what it needs to do if it finds the target. However, you then have to put in the necessary work to put that bullet where it needs to go to do it.

About The Author

Writer sam hoober