Центробойные патроны: устройство, история и преимущества

Type of ammunition that is commonly found in small , medium , and large caliber firearms

A center fire (or centerfire) is a type of metallic cartridge used in firearms, where the primer is located at the center of the base of its casing (i. e. "case head"). Unlike rimfire cartridges, the centerfire primer is typically a separate component seated into a recessed cavity (known as the primer pocket) in the case head and is replaceable by reloading the cartridge. Centerfire cartridges have supplanted the rimfire cartridge, with the exception of a few small calibers. The majority of today's handguns, rifles, and shotguns use centerfire ammunition, with the exception of some .17 caliber, .20 caliber, and .22 caliber rimfire handgun and rifle cartridges, a few small bore/gauge shotgun shells (intended mainly for use in pest control), and a handful of antiquated rimfire and pinfire cartridges for various firearm actions.

An early form of centerfire ammunition, without a percussion cap, was invented between 1808 and 1812 by Jean Samuel Pauly. This was also the first fully integrated cartridge and used a form of obturation employing the cartridge itself. Another form of centerfire ammunition was invented by the Frenchman Clement Pottet in 1829; however, Pottet would not perfect his design until 1855. The centerfire cartridge was improved by Béatus Beringer, Benjamin Houllier, Gastinne Renette, Smith & Wesson, Charles Lancaster, Jules Félix Gévelot, George Morse, Francois Schneider, Hiram Berdan and Edward Mounier Boxer.

Centerfire cartridges are more reliable for military purposes because the thicker metal cartridge cases can withstand rougher handling without damage, and is safer to handle because explosive priming compound in a protruding rim is more likely to be triggered by impact if a rimfire cartridge is dropped or pinched. The stronger base of a centerfire cartridge is able to withstand higher chamber pressures which in turn gives bullets greater velocity and energy. While centerfire cartridge cases require a complex and expensive manufacturing process, explosive handling is simplified by avoiding the spinning process required to uniformly distribute priming explosive into the rim because of uncertainty about which angular segment of a rimfire cartridge rim will be struck by the firing pin. Larger caliber rimfire cartridges require greater volumes of priming explosive than centerfire cartridges, and the required volume may cause undesirably higher pressure spikes during the ignition process. Reducing the amount of priming explosive will greatly diminish the ignition reliability of rimfire cartridges, and increase the probability of a malfunction such as a misfire or hang fire. Economies of scale are achieved through interchangeable primers for a wide variety of centerfire cartridge calibers. The expensive individual brass cases can be reused after replacing the primer, gunpowder and projectile. Handloading reuse is an advantage for rifles using obsolete or hard to find centerfire cartridges such as the 6.5×54mm Mannlicher–Schönauer, or larger calibers such as the .458 Lott, for which ammunition can be expensive. The forward portion of some empty cases can be reformed for use as obsolete or wildcat cartridges with similar base configuration. Modern cartridges larger than .22 caliber are mainly centerfire. Actions suitable for larger caliber rimfire cartridges declined in popularity until the demand for them no longer exceeded manufacturing costs, and they became obsolete.

The identifying feature of centerfire ammunition is the primer which is a metal cup containing a primary explosive inserted into a recess in the center of the base of the cartridge. The firearm firing pin crushes this explosive between the cup and an anvil to produce hot gas and a shower of incandescent particles to ignite the powder charge. Berdan and Boxer cartridge primers are both considered "centerfire" and are not interchangeable at the primer level; however, the same weapon can fire either Berdan or Boxer primed cartridges if the overall dimensions are the same. The two primer types are almost impossible to distinguish by looking at the loaded cartridge, though the two (or more) flash holes can be seen or felt inside a fired Berdan case and the larger single hole seen or felt inside a fired Boxer case. Berdan priming is less expensive to manufacture and is more commonly found in military surplus ammunition made outside of the United States.

Berdan primers are named after their American inventor, Hiram Berdan of New York who invented his first variation of the Berdan primer and patented it on March 20, 1866, in A small copper cylinder formed the shell of the cartridge, and the primer cap was pressed into a recess in the outside of the closed end of the cartridge opposite the bullet. In the end of the cartridge beneath the primer cap was a small vent hole, as well as a small teat like projection or point (this was to be known as an anvil later on) fashioned from the case, such that the firing pin could crush the primer against the anvil and ignite the propellant. This system worked well, allowing the option of installing a cap just before use of the propellant loaded cartridge, as well as permitting reloading the cartridge for reuse. Difficulties arose in practice because pressing in the cap from the outside tended to cause a swelling of the copper cartridge shell, preventing reliable seating of the cartridge in the chamber of the firearm. Berdan's solution was to change to brass shells, and to further modify the process of installing the primer cap into the cartridge, as noted in his second Berdan Primer patent of September 29, 1868, in Berdan primers have remained essentially the same functionally to the present day. Berdan primers are similar to the caps used in the caplock system, being small metal cups with pressure sensitive explosive in them. Modern Berdan primers are pressed into the "primer pocket" of a Berdan type cartridge case, where they fit slightly below flush with the base of the case. Inside the primer pocket is a small bump, the "anvil", that rests against the center of the cup, and usually two (or more) small holes by the sides of the anvil, which allow the flash from the primer to reach the interior of the case. Berdan cases are reusable, although the process is rather involved. The used primer must be removed, usually by hydraulic pressure, pincer, or lever that pulls the primer out of the bottom. A new primer is carefully seated against the anvil, and then the powder and a bullet are added.

From the 1880s to the 1940s, many smaller European armies were reloading their ammo for economical reasons, and for that reason they adopted the system known as either Austrian or after the George Roth factory in Vienna which patented it in 1902 even though it was known from the early to mid 1880s, where the anvil had a single fire hole right at its center.

All modern shotgun shells (excluding specialized .22 caliber rimfire "snake loads" or birdshot cartridges) are centerfire. They use a large, specific shotgun primer that is based on the Boxer system, in that the primer contains the anvil against which the primary explosive is compressed by the firing pin and deformation of the primer cup. Shotgun primers are also used as a replacement to the percussion cap ignition system in some modern black powder firearms, and in some cases as the actual cartridge, notably the 6mm Pipet.

Primer actuated or piston primer cartridges use a primer in the form of a blank to contain the propellant within an empty cartridge, or in some cases as a piston to unlock the bolt and operate the weapon. These types of rounds are rarely used and are mostly found on spotting rifles.