Editing Centerfire ammunition (section)

==Primers==
[[Image:45 ACP - FMJ - SB - 3.jpg|thumb|The primer of this unfired cartridge has been sealed with red [[lacquer]] to prevent oil or moisture from reaching the powder charge and priming explosive.]]
[[File:Berdan vs boxer2.jpg|thumb|Berdan (left) and Boxer (right) primed rifle cartridges]]

The identifying feature of centerfire ammunition is the [[Primer (firearm)|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.<ref name="nra65">[[William C. Davis, Jr.|Davis, William C., Jr.]] ''Handloading'' (1981) National Rifle Association of America p.65</ref>  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.<ref name="SAAMI">[[Sporting Arms and Ammunition Manufacturers' Institute]]</ref>

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.

===Benét primer===
Invented by [[Stephen Vincent Benét (general)|Stephen Vincent Benét]] in 1868,<ref>{{cite journal |last1=Clark |first1=Maj. Jerome |title=The Invention of the Central-Fire Primer |journal=The American Rifleman |date=May 1931 |pages=49}}</ref> this is placed and hidden internally within the base of the cartridge.

===Berdan primer===
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 {{US patent|53388}}. 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 {{US patent|82587}}. 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.

====Centered single-hole primer====
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<ref>{{patent|AT|15483B}}, diagram at [https://forum.cartridgecollectors.org/t/austrian-berdan-primers/13116/23]</ref> even though it was known from the early-to-mid 1880s, where the anvil had a single fire hole right at its center.

===Boxer primer===
[[file:Primers.jpg|thumb|Large (top row) and small (bottom row) pistol cartridge Boxer primers. (L–R fired, unfired, and inside view.) The tri-lobe object inside the primer is the anvil.]]
[[file:.45 ACP primers.jpg|thumb|The same cartridge ([[.45 ACP]] shown here) can have different primer sizes depending on manufacturer.]]

Meanwhile, Colonel [[Edward Mounier Boxer]], of the [[Royal Arsenal]], Woolwich, England, was working on a primer cap design for cartridges, patenting it in England on October 13, 1866, and subsequently received a U.S. patent for his design on June 29, 1869, in {{US patent|91,818}}.

Boxer primers are similar to Berdan primers with one major difference, the location of the anvil. In a Boxer primer, the anvil is a separate stirrup piece that sits inverted in the primer cup and provides sufficient resistance to the impact of the firing pin as it indents the cup and crushes the pressure-sensitive ignition compound. The primer pocket in the case head has a single flash-hole in its center. This positioning makes little or no difference to the performance of the cartridge, but it makes fired primers vastly easier to remove for [[Handloading|reloading]], as a single, centered rod pushed through the flash hole from the open end of the case will eject the two-piece primer from the primer cup. A new primer, anvil included, is then pressed into the case using a reloading press or hand-tool. Boxer priming is universal for US-manufactured civilian factory ammunition.

Boxer-primed ammunition is slightly more complex to manufacture, since the primer is in two parts in addition to the pressure-sensitive compound, but automated machinery producing the more complex primers by the hundreds of millions has eliminated that as a practical problem. And while the primer has one additional step needed during the manufacturing process, the cartridge case is simpler to make, use, and reload.

Early primers were manufactured with various dimensions and performance.  Some standardization has occurred where [[economies of scale]] benefit ammunition manufacturers. Boxer primers for the United States market come in different sizes, based on the application. The types/sizes of primers are:

* 0.175" (4.45&nbsp;mm) diameter ''small pistol'' primers, and a thicker or stronger metal cup ''small rifle'' version for use with higher pressure loadings in weapons with heavy firing pin impact.
* 0.209" (5.31&nbsp;mm) diameter primers for [[shotgun shell]]s and modern inline [[muzzleloader]]s, using a Boxer-type primer factory-assembled inside a tapered, flanged brass cup.
* 0.210" (5.33&nbsp;mm) diameter ''large rifle'' primers, and a thinner or softer metal cup ''large pistol'' version for use with lower pressure loadings in weapons with light firing pin impact. Large rifle primers are also 0.008" taller than large pistol primers.<ref>{{cite web|title=FAQ|url=http://www.cci-ammunition.com/education/faqs.aspx|access-date=27 March 2014|url-status=live|archive-url=https://web.archive.org/web/20140327053515/http://www.cci-ammunition.com/education/faqs.aspx|archive-date=27 March 2014}}</ref><ref>{{cite journal|last=Calhoon|first=James|title=Primers and Pressure|journal=Varmint Hunter|date=October 1995|url=http://www.jamescalhoon.com/primers_and_pressure.php|url-status=live|archive-url=https://web.archive.org/web/20150107135641/http://www.jamescalhoon.com/primers_and_pressure.php|archive-date=2015-01-07}}</ref>
* 0.315" (8.00&nbsp;mm) diameter [[.50 BMG]] primers, used for the .50 Browning Machine Gun cartridge and [[wildcat cartridge|derivatives]]
Examples of uses:
* [[.38 Special]], small pistol standard
* [[.357 Magnum]], small pistol magnum
* [[.45 Colt]], large pistol standard
* [[.50 Action Express]], large pistol magnum
* [[.223 Remington]], small rifle standard
* [[.357 Remington Maximum]], small rifle magnum
* [[.308 Winchester]], large rifle standard
* [[.338 Lapua Magnum]], large rifle magnum

Primer size is based on the primer pocket of the cartridge, with standard types available in large or small diameters.  The primer's explosive charge is based on the amount of ignition energy required by the cartridge design; a standard primer would be used for smaller charges or faster-burning powders, while a magnum primer would be used for the larger charges or slower-burning powders used with large cartridges or heavy charges. Rifle, large and magnum primers increase the ignition energy delivered to the powder, by supplying a hotter, stronger and/or longer-lasting flame. Pistol cartridges often are smaller than modern rifle cartridges, so they may need less primer flame than rifles require. A physical difference between pistol and rifle primers is the thickness of the primer's case; since pistol cartridges usually operate at lower pressure levels than most rifles, their primer cups are thinner, softer, and easier to ignite, while rifle primers are thicker and stronger, requiring a harder impact from the [[firing pin]].<ref>Lyman ''Ideal Hand Book No. 36''. Lyman Gun Sight Corporation (1949) p. 45.</ref>  Despite the names ''pistol'' and ''rifle'', the primer used depends on the cartridge, not the firearm; a few high-pressure pistol cartridges like the [[.221 Fireball]] and [[.454 Casull]] use rifle primers, while lower-pressure pistol and revolver cartridges like the .32 ACP, .380 ACP, 9mm Parabellum, .38 Special, .357 Magnum, .44 Magnum, and .45 ACP, and traditional [[revolver]] cartridges like the .32-20, .44-40, and .45 Colt, also used in [[lever-action]] rifles, these cartridges would still be loaded with pistol primers. Virtually all cartridges used solely in rifles do, however, use rifle primers. Notable exceptions to this include [[.458 SOCOM]] and [[.50 Beowulf]], which use large pistol standard and large pistol magnum primers, respectively.

===Shotgun primers===
[[Image:Pistol and shotgun primers.jpg|thumb|right|A fired pistol case as indicated by the dimple from a firing pin and a shotgun (right) primer against an inch and mm scale.]]

All modern [[shotgun shell]]s (excluding specialized .22 caliber rimfire [[Snake shot|"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]].<ref>{{Cite web|url=https://www.thefirearmblog.com/blog/2018/09/25/6mm-pipet-turkish-shotshell/|title=Turkish Small-Bore Shotshells Called 6mm Pipet -|date=25 September 2018}}</ref>

===Cartridge primers===
Primer actuated or piston primer cartridges use a primer in the form of a [[Blank (cartridge)|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 rifle]]s.<ref>{{Cite web|url=https://cartridgecollectors.org/cmo/cmo05oct.htm|title=Cartridge of the Month}}</ref><ref>{{Cite web|url=https://cartridgecollectors.org/cmo/cmo08dec.htm|title=Cartridge of the Month}}</ref><ref>{{Cite web|url=http://militarycartridges.nl/uk/9mm_smaw.htm|title = 7mm_compromise}}</ref><ref>{{cite web | title=Cartridge Details: 9 x 51mm SMAW Tracer MK217 Mod 0 United States | website=cartrology.com | url=http://www.cartrology.com/cartridges/627 | access-date=12 October 2023}}</ref>