From the moment a bullet is fired from a gun till it reaches its intended target, a lot of events take place, all in a split second. The accuracy and impact delivered by the bullet depends heavily on the way it is designed. Although bullets come in a wide variety of design and sizes, the basic principles on which they work remain the same.
Before we can understand how a bullet actually works, it is necessary to learn about the design as well as components of a bullet.
Design of a Bullet
Although the word bullet is often used synonymously with a cartridge, what we see as a bullet is actually just one of the components of a cartridge. A cartridge is the complete package consisting of the bullet, and other parts like the gunpowder and the case. The designs of bullets have undergone a sea change over the past decades. Today, all bullets usually come as part of a cartridge. A cartridge is sometimes also called a round, or a shell. There are many types of cartridges, but the basic design usually consists of four parts as shown below:
The bullet acts as a projectile that shoots out of the gun and hits the target.
The primer is a small cap at the base of the cartridge, containing a compound that explodes to ignite the propellant.
The propellant is an explosive substance, like gunpowder, that burns rapidly to create a huge amount of gas pressure to propel the bullet out of the bore of the gun.
The case holds all the parts i.e. bullet, propellant, and primer together, and is usually made of brass.
How Does a Bullet Work?
Now let's understand the mechanism of how a bullet works in a step-by-step manner. To explain in a nutshell, when the bullet is loaded into the barrel and the trigger is pulled, the following chain of events take place:
➡ The firing pin of the gun strikes and ignites the compound of the primer.
➡ The primer ignites the gunpowder contained in the cartridge, which burns to create huge gas pressure.
➡ The pressure thus created forces the bullet out of the barrel opening at a very high speed towards the target.
Now let's look at the above steps one-by-one in greater detail:
Step 1. The Trigger is Pulled
To begin with, the bullet is loaded into the firing chamber of the gun. The diameter of the cartridge is such that it fits the barrel of the gun exactly, and thus prevents the explosive gas from leaking out through the front opening of the barrel. When one pulls the trigger, the firing pin moves forward and strikes the primer hard. The compound in the primer explodes, releasing a flame.
Step 2. The Gunpowder is Ignited
The gunpowder acts as the propellant that pushes the bullet forward. The flame released from the primer ignites the explosive material of the propellant. The gunpowder explodes rapidly and releases gases that create a huge amount of pressure behind the bullet.
Step 3. The Bullet is Shot!
The mechanism of firing a bullet is based on Newton's third law of motion, which implies that for every action, there is an equal and opposite reaction. So, when the propellant burns, the resulting gas exerts a great force on the bullet. As there is no way out of the barrel except its open end, the bullet shoots forward and out of the barrel opening with a great velocity, leaving behind the cartridge and exhaust.
In some guns, the barrel has grooves on the inside, which provides a spin to the motion of the bullet, thereby leading to a more stable and straight line of flight. The impact of the bullet on the target depends upon the pressure that builds up due to the burning of the propellant.
Impact of a Bullet
After a bullet leaves the barrel, it needs to fulfill its ultimate aim of causing damage to the intended target. For this purpose, the bullet has to be both accurate as well as powerful enough to reach and penetrate the target.
The bullet does not follow a straight line trajectory due to gravity pulling it down to the earth. Another obstacle is air resistance, called drag, that slows the bullet down. Therefore, bullets usually have a pointed nose and a boat tail, that gives them a more streamlined motion.
The ability of a bullet to penetrate and damage its target depends on its size as well as its velocity. Although the bullets are small, they make up for their mass by high velocity, resulting in a higher momentum that is great enough to pierce the target. All this happens in a split second, which is why when seen through our eyes, the bullet seems to reach the target as soon as we hear the gunshot!