Eli5 : What are the dimensions mentioned in ammunitions? And how are they different from each other and what makes each one of them unique?

Question

In most movies and video games I have observed people mentioning ammo type and capacity such as, 5.56, 7.76, 9mm, 0.50 calibrate, .45 ACP.

What are these ammo type ?

Edit1: 0.50 Calibre, my mistake!

In: Engineering

Answer 1

There are lots and lots and lots of different cartridges for guns.

The history and reasons for which, will take far too long to go into. But basically, the numbers that bullets get is to do with their size.

There’s two bunches of sizes of bullets, there’s metric (in mm and grams) and imperial (in calibre which is fractions of an inch, and in grains)

there’s also two TYPES of ammo, generally. Rifle rounds, and pistol rounds.

Rifle rounds aren’t actually much bigger bullets than pistol bullets. But they have much much bigger cases, with way more space for gunpowder, which means they fly FASTER.

.50AE and .50BMG are good examples. One is a pistol round and one is a rifle round. They are the same thickness (half an inch), but one goes way way way faster. Google for images for a look.

But yeah, they’re just different sizes and shapes and fly differently. – there’s loads of resources online if you want to get deeper into it, but you just learn the different main types and then it all makes sense.