Hi andy_o,

Skeeter 7mm pretty much hit the nail on the head. Belted cases have an additional "ring" or "belt" near the bottom of the case just above the base or web.

And in case you are wondering why?

The belt is put there for headspacing. When a cartridge enters the chamber of a firearm it is necessary that is "properly positioned in the chamber"...or headspaced in order to fire. Some cartridges (like the .30-30 Winchester and .45-70...as well as revolver cartridges like the .38 Special, .44 Magnum, etc....to name only a few) "headspace" on a rim. So they are known as "Rimmed cartridges". Some other cartridges (like the .270 Winchester, .30-06 Springfield, .22-250, .243 Winchester, etc....once again to name only a few) "headspace" on their shoulder. They are typically referred to as "Standard cartridges". Some cartridges (like the .300 Weatherby, .300 Winchester, 7mm Remington Magnum, etc...to name a few) "headspace" on a belt. They are referred to as "Belted cartridges". And some cartridges, (mostly pistol....like the .380 ACP, .45 ACP, 9mm Parabellum, etc....to name a few) "headspace" on the case mouth.

For a better explanation of these and many other "firearms related terms" check out this site:

http://www.chuckhawks.com/index2.guns.htm

I hope this information has helped...rather than confused!