There are two classes of ammunition that you will encounter during your shooting days. Rimfire and centerfire.
Comparing the two is like comparing cars.
They do the same thing and get the same result, but they vary in how they do it. The primer is struck, which ignites the powder and the round is fired.
The only difference is where the primer is. You guessed it! Rimfire has the primer on the rim of the casing and centerfire is in the center.
However, there is more to it than just the location of the primer. Each type of cartridge serves different purposes.
When you come across a rimfire cartridge, it will pretty much always be a small caliber. 22 LR is the most common, but you will also find it in others, like .17. They do make large caliber rimfire cartridges, but they are rare as the higher pressure will destroy the casing.
Rimfire has a flat rim on the bottom of the case. This is where the primer is struck when you pull the trigger of your gun. The reason that rimfire is mainly limited to small calibers is because of this.
They use a cheap and weak brass to shape the casing, so once the round has been fired it cannot be reloaded or reused. If you’re looking to reload your own ammunition, stay away from rimfire.
However, the plus side to the weak brass is that manufacturing costs are lowered, which is why rimfire ammunition will costs you pennies. As always, low costs equal low reliability and rimfire is notorious for having issues with firing. Never use gun for protection that takes rimfire.
Centerfire cartridges will make up the rest of the ammunition that you come across. They will be the most common rounds that you see and are used for the majority of firearms.
Centerfire will encompass all of your self-defense rounds (9mm, .40, .45) and also your common rifle rounds (5.56, .223, 7.62). Centerfire cartridges are made to fire bigger caliber rounds than its counterpart.
Unlike rimfire, the brass that is used is much sturdier. When you fire a centerfire cartridge, you can reload it and shoot it again. It is as easy as putting in a new primer, more gun powder, and crimping it.
If you look at the bottom of the case, you will see a small object that looks like a pin. This is where the round is struck and it does not deform or bend the casing.
Centerfire is much more reliable because of this and should always be your choice when used for self-defense. However, the price of centerfire is much higher than rim.
They each have their pros and cons. Rimfire is good for practicing because it is cheap and centerfire is reliable if you need to use it. It is a good idea to have both in your arsenal and understand the differences between them. This will help you use them appropriately when you need to.