For some of you new shooters, here is some rifle terminology. I posted it as a reply on another thread, but thought it should be on a new thread so more of you can see it. Hope it's useful.
Here's the scoop on some of these terms:
action refers to the mechanism that moves the cartiridges through the rifle - from the magazine and into/out of the chamber. A bolt action does this by means of a handle that's connected directly to the side of the bolt; lever actions use a lever (usually part of the trigger guard) that's connected to a linkage system that connects to the bolt; semi-autos usually use a gas-porting and spring mechanism that are located inside the forearm; pump actions have a forearm that slides a linkage that connects to the bolt.
chamber refers to that part of the barrel where the cartridge is located during the actual firing of the rifle.
bullet refers to the part of the cartridge that actually leaves the muzzle. (Although by tradition it is also used to mean the whole cartridge.)
cartridge refers to the assembled bullet, powder, case (shell) and primer.
caliber refers to the size of the bullet - the diameter - although in the U.S. this is not always the case. Example: in 30/06 the "30" stands for the bullet diameter (actually .308 inch) and the "06" stands for the year (1906) that this cartridge was made the standard for the U.S. military rifle. This sometimes can get really confusing when you consider that the 44 Rem mag actually measures .429 inch; the 30/30 Win measures .307 ; the .270 Win measures .277; the .280 Rem measures .284, etc. The 30/06, 300 Savage, 300 Weatherby mag, 308 Win., 300 Win. mag, .308 Norma mag, 300 WSM, and several other rifles shoot the exact same .308 inch diameter bullet, but the cartridges are NOT interchangeable because the cases and chambers are all different sizes. Then because we all like to make life a little easier and faster, we compound this situation by shortening names. For example: we call the 7mm Rem magnum the "7mm" but there are a whole bunch of 7mms - even the .280 Rem is a 7mm. The European system of using millimeters is more accurate. For example: the 7 mm bullet actually has a 7mm diameter; the 6mm measures 6mm, etc.
As for magnums: the easiest way to explain this is that "magnum" usually means nothing more than a case or shell that has a relatively large powder capacity. Which usually means higher velocities from the same diameter bullets. For example (and putting this all together): because it's case is much larger, the .300 Win. magnum shoots its .308 diameter bullet several hundred feet per second faster than the same bullet out of the 30/06 or the .308 Win. Magnums are used when hunting dangerous game, but also in situations where especially long shots may be required. However, most cartridges that are considered suitable for big game, in the first place, can do as well as magnums under most circumstances.
Hope this helps.