Science of Fortnite

What is the difference between a semiautomatic and an automatic weapon?

The simple, functional answer is that an automatic weapon requires only that the trigger be pulled for the weapon to keep firing, while a semiautomatic weapon requires that the trigger be pulled each time a bullet is fired. Both of these are different from a manual weapon, which requires some form of action to be taken by the shooter between each shot, whether pulling back the hammer on the revolver, a bolt on a hunting rifle, etc.

While there are many different types of technologies that make some guns automatic and others semiautomatic, most semiautomatic guns are simply automatic guns in which an extra pin has been added to stop the bolt from shooting forward after it is compressed back, until the trigger is pulled again. In this sense, most semiautomatic weapons actually employ extra functionality to stop themselves from being fully automatic.

Why do some automatic weapons fire faster than others, and why don’t they just make all semiautomatic weapons automatic?

First and foremost, the decision to make a gun automatic versus semiautomatic is mostly made based on the intended uses of the weapon itself. Even apart from the fact that automatic weapons are generally illegal most places in the civilized world, there are many use-cases in which it is simply not ideal to shoot more than one round with each pull of the trigger. This can be due to the user wanting to limit the amount of damage being caused, or just as a means for conserving ammunition. This second reason is especially common: an automatic weapon obviously burns through ammunition much faster than a semiautomatic weapon does, and, unlike in Fortnite, real-world ammunition is heavy, expensive, and generally quite limited.

Similarly, the rate of fire of a fully automatic weapon is at least partially determined by the intended use of the weapon. The faster an automatic weapon fires, the more damage it does, and the more ammo it uses. Any situation where you want to do less damage and/or use less ammo will necessitate a slower rate of fire.

That said, from a technical standpoint, the rate of fire of an automatic weapon is also limited largely by the heat that the gun generates as it fires. Each time a bullet is fired, a small explosion takes place inside a gun, and 3,000-plus-degree gases are shot through the barrel. The higher the rate of fire of an automatic weapon, the hotter the barrel is going to get, and the less time it has to cool between each shot. Gun designers have found many ways to mediate this heat problem, including using air and/or water to cool the barrel, but no matter how it is dealt with, every gun will have a limit as to how much heat the barrel can handle from continuous automatic firing before the gun fails and stops working.