This is a fairly random post. I was listening to a radio program of a knowledgeable guy who repeatedly called the magazine of a pistol the "cartridge." Now, he's been in radio for a long time, so I'm sure he remembers inserting cartridges into players and he blanked on the proper term. Still, since so many people really don't have much knowledge of terminology, I thought I'd toss up a post on it.
People often refer to the part of the firearm that holds rounds of ammunition as a "clip." That's not exactly right. Here's a picture to help:
A clip is actually a device that holds rounds of ammunition in a convenient way so that they can be inserted into the internal magazine of a firearm. In the above picture, the clip is the silver strip holding the ends of the rounds (those look like 7.62 x 39 mm, and I've used a similar clip to quickly load an SKS rifle for a match). The rounds are often slid off of the clip into the magazine. The clip just makes them easy to load.
Clip loading systems have mostly been replaced by the more modern box magazine. That's the recognizable black thing on the right above. A detachable box magazine (people often just call them "mags") holds rounds of ammunition, and can be quickly inserted into a firearm. It's quicker than a clip. Below is an example of a pistol magazine (the one above is a rifle magazine).
Really high capacity magazines are usually called drum magazines, which is no shock given what they look like. In the below image it's the part sticking out below the rifle below where you'd normally see a normal box or banana magazine hanging out, forward of the grip and trigger guard.
You may have noticed I'm calling those things the gun fires rounds of ammunition. Most people call them bullets. That's not quite right. Here's a bullet (below):
It's just the small piece of metal that flies out of the end of the gun. The pictured bullet is a hollowpoint handgun bullet. Rifle bullets are often longer and more pointed (though some handgun bullets are designed to come to a sharper point, too).
Here are a couple of rounds of ammunition:
Rounds consist of several parts. The shiny brass part is the shell casing (you can also call rounds shells or ammo for short). The top part is the bullet. Inside there will be gunpowder and at the bottom end, a primer that ignites the gunpowder when struck by the firearm's firing pin. In a semiautomatic firearm, the casing will be ejected out of the side. In a revolver or bolt action rifle, the casing is manually removed with the aid of an extractor.
While this isn't the most exciting post you'll ever read, now you can wow your friends with all your impressive knowledge of terminology.