The Science Behind Ammunition: Bullets and Terminal Ballistics

Do you wonder what happens in that split second between pulling the trigger and the bullet flying out of the barrel? Or why do some bullets cause more damage than others?

The good news is, you don’t need to wonder anymore. By the time you finish reading this article, you will know exactly how bullets work and understand the science behind terminal ballistics.

There’s no time like the present, so let’s get right on it!

How Bullets Work

To understand how bullets work, we have to explain their anatomy first.

Let’s get the obvious thing out of the way. As you can see in the image above, a bullet is a projectile that flies out of the barrel. A single piece of ammunition is actually called a cartridge or round. To avoid any confusion from this point on, whenever we mention a bullet, we will refer to a projectile.

Other parts of the cartridge include:

  1. Primer, which consists of a copper or brass alloy cup and brass anvil. It is loaded with an impact-sensitive lead styphnate igniter.
  2. Propellant, a chemical substance responsible for expelling the bullet out of the barrel. It is usually a combination of gunpowder, nitrocellulose, and other ingredients.
  3. Cartridge case, which is the outer shell made of either brass or steel. It is designed to withstand high pressures.
  4. Metal jacket, which is the metal covering that encases the projectile and ensures that it has a consistent shape when fired. It is usually made of harder metals.
  5. Lead, which is the material of choice for most ammo. It is the soft core surrounded by the harder metal casing.
  6. Flash hole, which is a little hole that transfers the flash from the primer to the propellant.

When you pull a trigger, a spring makeeover mechanism strikes a metal firing pin into the rear end of the cartridge where the primer is placed. This causes the impact-sensitive powder inside the primer to explode. So when the flash from that explosion goes through the flash hole, it ignites the propellant.

As the propellant powder starts to burn, it gradually generates gas pressure. With all that pressure building up in the confined space, the generated energy searches for the weakest point to get out. And in cartridges, that weakest point is the joint between the bullet and the case.

Pushed by the sudden high pressure, the bullet flies through the barrel at high speed (2500fps on average) while the cartridge case stays in place.

The interesting thing is that it all seems to happen instantaneously. But in fact, the propellent powder burns relatively slowly, allowing a bullet to travel smoothly down the barrel.

And as the bullet accelerates, the propellent starts to burn faster, giving it an extra “kick” as it comes out of the barrel. This process is called deflagration, and it all happens in 2.6 to 9.0 milliseconds.

Now that you know how bullets work, let’s see what makes them so lethal.

Factors that Determine Bullets’ Terminal Ballistics

Terminal ballistics, aka wound ballistics, examines how a bullet behaves and how it transfers its kinetic energy upon hitting the target. Or simply put, what amount of damage it can cause to living tissue.

The seven determinants of a bullet’s terminal ballistics are its striking energy, striking velocity, penetration, bullet expansion, bullet tumbling, and bullet rotation velocity.

Here we’ll discuss the two main determining factors of a bullet’s terminal ballistics—striking energy and striking velocity.

Striking Energy

When a bullet strikes and penetrates the target, it transmits a portion or all of its kinetic energy to the target, making both the bullet and tissue deform in the process.

The bullet’s kinetic energy upon impact is used for measuring the cartridge’s power and is expressed in foot per pound (Ft-lbs) or joules (J) metrics.

Striking Velocity

The more distance the bullet travels, the more it starts to slow down. Striking velocity is the velocity measured at the moment the bullet hits the target.

At initial impact and penetration, a bullet forms a localized toonily zone of high pressure. This pressure displaces tissue particles onward from the impact point. And as the bullet keeps penetrating, it creates a permanent wound path.

On this path, the bullet may expand or tumble, causing a larger wound canal and creating secondary projectiles like bits of bones, pieces of clothing, etc., that can do even more damage.

When you double bullet weight, you double its striking energy. But when you double the bullet’s striking velocity, you quadruple its striking energy.

Closing Thoughts

Now that you know how bullets work and what makes them so deadly, you might be able to make more informed decisions when choosing the right ammo for your needs. Luckily, there are plenty of options to choose from in online shooting supplies stores, such as Natchez ammunition.

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