Editing Cartridge (firearms) (section)

==== Primer ====
[[File:Percussion caps.jpg|thumb|right|Percussion caps, the precursor of modern primers]]
[[File:Centerfire & rimfire ignition.gif|thumb|Comparison of primer ignition between centerfire (left two) and rimfire (right) ammunitions]]
[[File:Berdan vs boxer2.jpg|thumb|Flash hole profiles on Berdan (left) and Boxer (right) primers.]]
{{main|Primer (firearm)}}{{see also|Percussion cap}}
Because the main propellant charge is located deep inside the [[gun barrel]] and thus impractical to be directly lighted from the outside, an intermediate is needed to relay the [[fire making|ignition]]. In the earliest [[black powder]] [[muzzleloader]]s, a [[fuse (explosives)|fuse]] was used to direct a small flame through a [[touch hole]] into the barrel, which was slow and subjected to disturbance from environmental conditions. The next evolution was to have a small separate charge of finer gunpowder poured into a [[flash pan]], where it could start a "priming" ignition by an external source, when ignited the flame passed through a small hole in the side of the barrel to ignite the main gunpowder charge. 

The last evolution was to use a small [[percussion cap|metallic cap]] filled with a shock sensitive explosive compound that would ignite with a [[Hammer (firearms)|hammer]] strike. The source of ignition could be a burning [[slow match]] ([[matchlock]]) placed onto a [[touch hole]], a piece of [[pyrite]] ([[wheellock]])/[[flint]] ([[flintlock]]) striking a steel [[frizzen]], or a [[shock sensitivity|shock-sensitive]] brass or copper percussion cap ([[caplock]]) placed over a conical-shaped cone piece with a hollow pipe to create [[spark (fire)|spark]]s. When the primer powder starts combusting, the flame is transferred through an internal touch hole called a ''flash hole'' to provide [[activation energy]] for the main powder charge in the barrel. The disadvantage Is that the flash pan cAN still be exposed to the outside, making it difficult (or even impossible) to fire the gun in rainy or humid conditions as wet gunpowder burns poorly.

After [[Edward Charles Howard]] discovered [[fulminate]]s in 1800<ref>Howard, Edward (1800) [https://archive.org/details/bub_gb_dlFFAAAAcAAJ/page/n220 <!-- pg=204 --> "On a New Fulminating Mercury"], ''Philosophical Transactions of the Royal Society of London'' '''90''' (1): 204–238.</ref><ref>[https://www.npg.org.uk/collections/search/person/mp02292/edward-charles-howard Edward Charles Howard] {{Webarchive|url=https://web.archive.org/web/20210514052233/https://www.npg.org.uk/collections/search/person/mp02292/edward-charles-howard |date=14 May 2021 }} at National Portrait Gallery</ref> and the patent by [[Reverend]] [[Alexander John Forsyth]] expired in 1807,<ref name="Fadala2006">{{cite book|last=Fadala|first=Sam|title=The Complete Blackpowder Handbook|url=https://books.google.com/books?id=Dzxyneq43AEC&pg=PA160|date=17 November 2006|publisher=Gun Digest Books|location=Iola, Wisconsin|isbn=0-89689-390-1|pages=159–161}}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> [[Joseph Manton]] invented the precursor [[percussion cap]] in 1814,<ref>{{cite book|author=Sam Fadala|title=The Complete Blackpowder Handbook|url=https://books.google.com/books?id=Dzxyneq43AEC&pg=PA158|year=2006|publisher=Krause Publications|isbn=978-0-89689-390-0|page=158}}{{Dead link|date=November 2023 |bot=InternetArchiveBot |fix-attempted=yes }}</ref> which was further developed in 1822 by the English-born American artist [[Joshua Shaw]],<ref>{{cite web|url=http://www.researchpress.co.uk/firearms/ignition/shaw02.htm |archive-url=https://web.archive.org/web/20120218221926/http://www.researchpress.co.uk/firearms/ignition/shaw02.htm |url-status=dead |archive-date=18 February 2012 |title=Joshua Shaw |access-date=5 November 2018}}</ref> and [[caplock]] [[fowling piece]]s appeared in [[Regency era]] England. These guns used a [[spring (device)|spring]]-loaded [[hammer (firearms)|hammer]] to strike a percussion cap placed over a [[conical]] "nipple", which served as both an "[[anvil]]" against the hammer strike and a transfer port for the sparks created by crushing the cap, and was easier and quicker to load, more resilient to weather conditions, and more reliable than the preceding flintlocks.<ref name="Fadala2006"/>

Modern primers are basically improved percussion caps with [[shock sensitivity|shock-sensitive]] chemicals (e.g. [[lead styphnate]]) enclosed in a small button-shaped capsule. In the early [[paper cartridge]]s, invented not long after the percussion cap, the primer was located deep inside the cartridge just behind the bullet, requiring a very thin and elongated [[firing pin]] to pierce the paper casing. Such guns were known as [[needle gun]]s, [[Dreyse needle gun|the most famous of which]] was decisive in the [[Kingdom of Prussia|Prussia]]n victory over the [[Austrian Empire|Austria]]ns at [[Battle of Königgrätz|Königgrätz]] in 1866. After the metallic cartridge was invented, the primer was relocated backward to the base of the case, either at the center of the case head ([[centerfire]]), inside the rim ([[rimfire ammunition|rimfire]]), inside a cup-like concavity of the case base (cupfire), in a pin-shaped sideways projection ([[pinfire]]), in a lip-like [[flange]] ([[Ethan Allen (armsmaker)#Cartridge pistols|lipfire]]), or in a small nipple-like bulge at the case base ([[teat-fire]]). Today, only the centerfire and rimfire have survived as the mainstream primer designs, while the pinfire also still exists but only in rare novelty miniature guns and a few very small [[blank cartridge]]s designed as noisemakers.

In rimfire ammunitions, the primer compound is [[injection moulding|moulded]] integrally into the interior of the protruding [[rim (firearms)|case rim]], which is crushed between the firing pin and the edge of the barrel breech (serving as the "anvil"). These ammunitions are thus not [[handloading|reload]]able, and are usually on the lower end of the [[muzzle energy|power]] spectrum, although due to the low [[manufacturing cost]] some of them (e.g. [[.22 Long Rifle]]) are among the most popular and prolific ammunitions currently being used.

Centerfire primers are a separately manufactured component, seated into a central recess at the case base known as the ''primer pocket'', and have two types: Berdan and Boxer. Berdan primers, patent by American inventor [[Hiram Berdan]] in 1866, are a simple capsule, and the corresponding case has two small flash holes with a bulged bar in between, which serves as the "anvil" for the primer. Boxer primers, patented by [[Royal Artillery]] colonel [[Edward Mounier Boxer]] also in 1866, are more complex and have an internal tripedal "anvil" built into the primer itself, and the corresponding case has only a single large central flash hole. Commercially, Boxer primers dominate the [[handloading|handloader]] market due to the ease of depriming and the ability to transfer sparks more efficiently.

Due to their small size and charge load, primers lack the power to shoot out the projectile by themselves, but can still put out enough energy to separate the bullet from the casing and push it partway into the barrel – a dangerous condition called a [[squib load]]. Firing a fresh cartridge behind a squib load obstructing the barrel will generate dangerously high pressure, leading to a [[catastrophic failure]] and potentially causing severe injuries when the gun blows apart in the shooter's hands. Actor [[Brandon Lee]]'s [[The Crow (1994 film)#Brandon Lee's death|infamous accidental death in 1993]] was believed to be caused by an undetected squib that was dislodged and shot out by a [[blank (cartridge)|blank]].