Centerfire ammunition
A centerfire cartridge is a cartridge in which the primer is located in the center of the cartridge case head. Unlike rimfire cartridges, the primer is a separate and replaceable component.
The centerfire cartridge has replaced the rimfire in all but the smallest cartridge sizes. Except for low-powered .22 and .17 caliber cartridges, and a handful of antiques, all modern pistol, rifle, and shotgun ammunition are centerfire.
Advantages and disadvantages
The advantage of most centerfire cartridges is that they can be reused after replacing the primer, gunpowder and projectile. This is an advantage for rifles using cartridges that are obsolete or hard to find, e.g. the 6.5x54 Mannlicher, or larger calibers like .458 Lott for which ammunition can be quite expensive. Centerfires also are generally larger and capable of higher powered loads. Centerfire cartridges are more powerful since they can hold higher pressures than a similar rimfire cartridge, and thus they also are more efficient for their size. For target shooting purposes, centerfire cartridges are more expensive, but for applications involving the hunting of large game they are the best choice. Centerfires rule the market in all larger calibers, having replaced earlier large-bore rimfire cartridges.
Shotgun Gauges
Most shotgun gauges are center fire. However some small, older ones are rimfire. Originally shotgun shells were drawn brass but now most are made from plastic although some were and still are made of paper. All shotgun shells formed from brass and most formed from brass and plastic can be reloaded and used again, like all centerfire cartridges.
A shotgun shell consists of the brass hull, and the plastic or paper portion. The primer is set in the hull and ignites the powder. The explosion ejects the wad which contains the shot.