A cartridge, round, or cartridge is a type of pre-assembled firearm ammunition consisting of a projectile (bullet, shot, or slug), propellant substance (usually either smokeless powder or black powder), and ignition device (primer) all contained within a metallic, paper, or plastic case designed to fit within the barrel chamber of a breechloading gun.
Although “bullet” is commonly used to refer to an entire cartridge, technically speaking it only refers to the projectile.
Primers, which are small charges of an impact- or electric-sensitive chemical mixture, are commonly found in the following places on cartridges: the center of the case head (centerfire), the interior of the rim (rimfire), the interior of the walls on the fold of the case base that is shaped like a cup (cupfire, now obsolete), the tip of a side projection that is shaped like a pin (pinfire, now obsolete), the tip of a side projection that is shaped like a lip (teat-fire, now obsolete).
The only types of firearms still in common use are centerfire and rimfire.
Both government and private manufacturers are still working toward the development of caseless ammunition.
The cartridge concept used in some artillery ammunition is also used in handguns.
The artillery shell and the explosive charge are two different components in most cases.
A blank cartridge is one that has no projectile, a dummy cartridge has no active primer or propellant, and a dud cartridge fails to ignite and fire the projectile, while a squib cartridge ignites but fails to force the projectile far enough out of the barrel to be considered effective.