Centerfire ammunition
Encyclopedia
A centerfire cartridge is a cartridge with a primer located in the center of the cartridge case head. Unlike rimfire cartridges, the primer is a separate and replaceable component.
The centerfire cartridge has supplanted the rimfire in all but the smallest cartridge sizes. Except for low-powered .22 and .17 caliber cartridges, and a handful of antiques, all pistol
, rifle
, and shotgun
ammunition used today is centerfire.
Handloading
reuse is an advantage for rifles using obsolete or hard-to-find cartridges such as the 6.5x54 Mannlicher
, 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 cartridge
s with similar base configuration. Modern cartridges larger than .22 caliber are mostly 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—a metal cup containing 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 interchangeable; the same weapon can fire either Berdan- or Boxer-primed rounds if the cartridge dimensions are the same.
The two primer types are almost impossible to distinguish by looking at the loaded cartridge, though the two flash-holes can be seen 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 much more common in military-surplus ammunition made outside the United States.
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 (later to be known as an anvil) 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, 1869, 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 two small holes (one on either side of the anvil) that allow 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 or a pincer or lever that pulls the primer out of the bottom. A new primer is carefully seated against the anvil, and then gunpowder and a bullet are added.
, 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 .
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 providing sufficient resistance to the impact of the firing pin as it indents the cup crushing against 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 round, but it makes fired primers vastly easier to remove for re-loading; the spent primer assembly is removed by pushing a thin metal rod through the flash hole from the open end of the case. A new primer, anvil included, is then pressed into the case using a reloading press or hand-tool. Since the primer cup, ignition compound and anvil are together as one piece, the anvil depth must be the correct match for the primer that is being inserted, so that the primer does not suffer excessive crushing potentially causing ignition (priming is done as the first step, after cleaning and resizing the empty case before the powder is added). Boxer priming is universal for civilian factory ammunition, and contributes to the large number of shooters who reload their ammunition.
Boxer-primed ammunition is slightly more complex to manufacture, since the primer is in two parts with a drop of pressure sensitive compound, but automated machinery producing primers by the hundreds of millions has eliminated that as a practical problem and while the primer is one step more complex to make, the cartridge case is simpler to make, use and maintain. For users who buy brass cases for reloading, the initial cost is more than equalised by the decreased cost of firing reloaded rounds compared to buying factory loaded ammunition, which is often an excellent source of reusable brass (reloading ammunition can save significant costs compared with new factory rounds).
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:
Examples of uses:
The 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 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
. (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 and .380 Autos, 9mm Luger, .38 Special, .357 Magnum, .44 Magnum and .45 ACP and traditional revolver
cartridges like .32-20, .44-40 and .45 Colt, also used in lever action rifles, still would be loaded with pistol primers. Virtually all cartridges used solely in rifles do, however, use rifle primers.)
ammunition firm. Modern commercial operations use protective shielding between operators and manufacturing equipment.
Early primers used the same mercury fulminate used in 19th century percussion caps. Black powder could be effectively ignited by hot mercury
released upon decomposition. Disadvantages of mercuric primers became evident with smokeless powder
loadings. Mercury fulminate slowly decomposed in storage until the remaining energy was insufficient for reliable ignition. Decreased ignition energy with age had not been recognized as a problem with black powder loadings because black powder could be ignited by as little energy as a static electricity discharge. Smokeless powder often required more thermal energy for ignition. Misfires and hang fire
s became common as the remaining priming compound sputtered in old primers. A misfire would result if the priming compound either failed to react to the firing pin fall or extinguished prior to igniting the powder charge. A hang fire is a perceptible delay between the fall of the firing pin and discharge of the firearm. In extreme cases, the delay might be sufficient to be interpreted as a misfire, and the cartridge could fire as the action was being opened or the firearm pointed in an inappropriate direction.
Incandescent particles were found most effective for igniting smokeless powder after the primary explosive gasses had heated the powder grains. Artillery charges frequently included a smaller quantity of black powder to be ignited by the primer, so incandescent potassium carbonate
would spread fire through the smokeless powder. Potassium chlorate
was added to priming mixtures so incandescent potassium chloride
would have a similar effect in small arms cartridges.
Priming mixtures containing mercury fulminate leave metallic mercury in the bore and empty cartridge case after firing. The mercury was largely absorbed in the smokey fouling with black powder loads. Mercury coated the interior of brass
cases with smokeless powder loads, and the higher pressures of smokeless powder charges forced the mercury into grain boundaries between brass crystals where it formed zinc
and copper
amalgams
weakening the case so it became unsuitable for reloading. The United States Army
discontinued use of mercuric priming mixtures in 1898 to allow arsenal reloading of fired cases during peacetime. Frankford Arsenal
primers used a mixture of potassium chlorate and antimony sulfide
through the first half of the 20th century. These corrosive primers leave a residue of potassium chloride salt in the bore after a cartridge is fired. These hygroscopic salt crystals will hold moisture from a humid atmosphere and cause rusting. These corrosive primers can cause serious damage to the gun unless the barrel and action are cleaned carefully after firing.
Civilian ammunition manufacturers began offering non-corrosive primers in the 1920s, but most military ammunition continued to use corrosive priming mixtures of established reliability. The various proprietary priming formulations used by different manufacturers produced some significantly different ignition properties until the United States issued military specifications for non-corrosive lead styphnate
primers for 7.62x51mm NATO cartridge production. Most United States manufacturers adopted the military standard for their civilian production of Boxer primers. Manufacturers subsequently offered more powerful magnum primers for uniform ignition of civilian long-range or big-game cartridges with significantly greater powder capacity than required for standard infantry weapons.
Other explosives used in primers include lead azide, potassium perchlorate
, or diazodinitrophenol (DDNP). New on the market in the late 1990s are lead-free primers, which address concerns over the lead and other heavy-metal compounds found in older primers. The heavy metals, while small in quantity, are released in the form of a very fine soot. Some indoor firing ranges are moving to ban primers containing heavy metals due to their toxicity. Lead-free primers were originally less sensitive and had a greater moisture sensitivity and correspondingly shorter shelf life than normal noncorrosive primers. Since their introduction, lead-free primers have become equal in performance to lead-based primers, and are gradually gaining popularity.
Military-surplus ammunition often uses inexpensive corrosive or slightly-corrosive Berdan primers because they work reliably under severe conditions, whereas modern Boxer primers are almost always non-corrosive and non-mercuric. Determination of corrosive or non-corrosive characteristics based on the primer type should consider these final headstamp
dates of corrosive ammunition production:
All shotgun shells (apart from specialized .22 cartridges which hold a very small amount of shot and 9mm rimfire) are center fire. Most are made from plastic although some were and still are made of paper. Shotgun shells, like most centerfire cartridges, can be reloaded and used again. 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. Shotgun primers for use in cold weather may contain magnum explosive charges to counteract the slower ignition and burning of powders at low temperatures.
The centerfire cartridge has supplanted the rimfire in all but the smallest cartridge sizes. Except for low-powered .22 and .17 caliber cartridges, and a handful of antiques, all pistol
Pistol
When distinguished as a subset of handguns, a pistol is a handgun with a chamber that is integral with the barrel, as opposed to a revolver, wherein the chamber is separate from the barrel as a revolving cylinder. Typically, pistols have an effective range of about 100 feet.-History:The pistol...
, rifle
Rifle
A rifle is a firearm designed to be fired from the shoulder, with a barrel that has a helical groove or pattern of grooves cut into the barrel walls. The raised areas of the rifling are called "lands," which make contact with the projectile , imparting spin around an axis corresponding to the...
, and shotgun
Shotgun
A shotgun is a firearm that is usually designed to be fired from the shoulder, which uses the energy of a fixed shell to fire a number of small spherical pellets called shot, or a solid projectile called a slug...
ammunition used today is centerfire.
Advantages
Centerfire cartridges are more reliable for military purposes, because the thicker metal cartridge cases can withstand rougher handling without damage. The stronger base of a centerfire cartridge is able to withstand higher pressures than a thin rimfire cartridge. Higher pressures give a bullet higher velocity and greater energy. While centerfire cartridge cases require a complex and expensive manufacturing process, economies of scale are achieved through interchangeable primers for similar cartridges. The expensive individual cases can be reused after replacing the primer, gunpowder and projectile.Handloading
Handloading
Handloading or reloading is the process of loading firearm cartridges or shotgun shells by assembling the individual components , rather than purchasing completely assembled, factory-loaded cartridges...
reuse is an advantage for rifles using obsolete or hard-to-find cartridges such as the 6.5x54 Mannlicher
6.5x54mm Mannlicher-Schönauer
The 6.5x54 Mannlicher-Schönauer also known as 6.5x54 Mannlicher-Schönauer Greek is a 6.5 mm rifle cartridge used in the Mannlicher-Schönauer rifle...
, or larger calibers such as the .458 Lott
.458 Lott
The .458 Lott is a .458 caliber belted hunting cartridge designed as a replacement for the less powerful .458 Winchester Magnum. It is based on the full length .375 H&H Magnum blown out and shortened to...
, for which ammunition can be expensive. The forward portion of some empty cases can be reformed for use as obsolete or wildcat cartridge
Wildcat cartridge
A wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...
s with similar base configuration. Modern cartridges larger than .22 caliber are mostly 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.
Centerfire primers
Firing pin
A firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...
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 interchangeable; the same weapon can fire either Berdan- or Boxer-primed rounds if the cartridge dimensions are the same.
The two primer types are almost impossible to distinguish by looking at the loaded cartridge, though the two flash-holes can be seen 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 much more common in military-surplus ammunition made outside the United States.
Berdan primer
Berdan primers are named after their American inventor, Hiram BerdanHiram Berdan
Hiram Berdan was an American engineer, inventor and military officer, world-renowned marksman, and guiding force behind and commanding colonel of the famed United States Volunteer Sharpshooter Regiments during the American Civil War...
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 (later to be known as an anvil) 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, 1869, 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 two small holes (one on either side of the anvil) that allow 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 or a pincer or lever that pulls the primer out of the bottom. A new primer is carefully seated against the anvil, and then gunpowder and a bullet are added.
Boxer primer
Meanwhile, Edward M. Boxer, of the Royal ArsenalRoyal Arsenal
The Royal Arsenal, Woolwich, originally known as the Woolwich Warren, carried out armaments manufacture, ammunition proofing and explosives research for the British armed forces. It was sited on the south bank of the River Thames in Woolwich in south-east London, England.-Early history:The Warren...
, 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 .
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 providing sufficient resistance to the impact of the firing pin as it indents the cup crushing against 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 round, but it makes fired primers vastly easier to remove for re-loading; the spent primer assembly is removed by pushing a thin metal rod through the flash hole from the open end of the case. A new primer, anvil included, is then pressed into the case using a reloading press or hand-tool. Since the primer cup, ignition compound and anvil are together as one piece, the anvil depth must be the correct match for the primer that is being inserted, so that the primer does not suffer excessive crushing potentially causing ignition (priming is done as the first step, after cleaning and resizing the empty case before the powder is added). Boxer priming is universal for civilian factory ammunition, and contributes to the large number of shooters who reload their ammunition.
Boxer-primed ammunition is slightly more complex to manufacture, since the primer is in two parts with a drop of pressure sensitive compound, but automated machinery producing primers by the hundreds of millions has eliminated that as a practical problem and while the primer is one step more complex to make, the cartridge case is simpler to make, use and maintain. For users who buy brass cases for reloading, the initial cost is more than equalised by the decreased cost of firing reloaded rounds compared to buying factory loaded ammunition, which is often an excellent source of reusable brass (reloading ammunition can save significant costs compared with new factory rounds).
Boxer primer sizes
- 0.175" (4.45 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 mm) diameter primers for shotgun shellShotgun shellA shotgun shell is a self-contained cartridge loaded with lead shot or shotgun slug designed to be fired from a shotgun....
s and modern inline muzzleloaderMuzzleloaderA muzzleloader is any firearm into which the projectile and usually the propellant charge is loaded from the muzzle of the gun . This is distinct from the more popular modern designs of breech-loading firearms...
s, using a Boxer-type primer factory-assembled inside a tapered, flanged brass cup. - 0.210" (5.33 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.
- 0.315" (8.00 mm) diameter .50 BMG.50 BMGThe .50 Browning Machine Gun or 12.7×99mm NATO is a cartridge developed for the Browning .50 caliber machine gun in the late 1910s. Entering service officially in 1921, the round is based on a greatly scaled-up .30-06 cartridge...
primers, used for the .50 Browning Machine Gun cartridge and derivativesWildcat cartridgeA wildcat cartridge, or wildcat, is a custom cartridge for which ammunition and firearms are not mass produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge.Developing and using wildcat cartridges does not...
Examples of uses:
- .38 Special.38 SpecialThe .38 Smith & Wesson Special is a rimmed, centerfire cartridge designed by Smith & Wesson. It is most commonly used in revolvers, although some semi-automatic pistols and carbines also use this round...
, small pistol standard - .357 Magnum.357 MagnumThe .357 S&W Magnum , or simply .357 Magnum, is a revolver cartridge created by Elmer Keith, Phillip B. Sharpe, Colonel D. B. Wesson of firearms manufacturer Smith & Wesson, and Winchester. It is based upon Smith & Wesson's earlier .38 Special cartridge. The .357 Magnum cartridge was introduced in...
, small pistol magnum - .45 ACP.45 ACPThe .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...
, large pistol standard - .223 Remington.223 RemingtonThe .223 Remington is a sporting cartridge with almost the same external dimensions as the 5.56×45mm NATO military cartridge. The name is commonly pronounced either two-two-three or two-twenty-three. It is loaded with a diameter, jacketed bullet, with weights ranging from , though the most common...
, small rifle standard - .308 Winchester.308 WinchesterThe .308 Winchester is a rifle cartridge and is the commercial cartridge upon which the military 7.62x51mm NATO centerfire cartridge is based. The .308 Winchester was introduced in 1952, two years prior to the NATO adoption of the 7.62x51mm NATO T65...
, large rifle standard - .270 WSMWinchester Short MagnumWinchester Short Magnum, or WSM, refers to a family of rebated rim bottlenecked centerfire short magnum cartridges developed in the early 2000s by the U.S. Repeating Arms Company, the maker of Winchester rifles and one of the oldest firearms manufacturers in the United States...
, large rifle magnum
The 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 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
Firing pin
A firing pin or striker is part of the firing mechanism used in a firearm or explosive device e.g. an M14 landmine or bomb fuze. Firing pins may take many forms, though the types used in landmines, bombs, grenade fuzes or other single-use devices generally have a sharpened point...
. (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
.454 Casull
The .454 Casull is a firearm cartridge, developed in 1957 by Dick Casull and Jack Fulmer. It was first announced in November 1959 by Guns & Ammo magazine. The basic design was a lengthened and structurally improved .45 Colt case...
use rifle primers, while lower-pressure pistol and revolver cartridges like the .32 and .380 Autos, 9mm Luger, .38 Special, .357 Magnum, .44 Magnum and .45 ACP and traditional revolver
Revolver
A revolver is a repeating firearm that has a cylinder containing multiple chambers and at least one barrel for firing. The first revolver ever made was built by Elisha Collier in 1818. The percussion cap revolver was invented by Samuel Colt in 1836. This weapon became known as the Colt Paterson...
cartridges like .32-20, .44-40 and .45 Colt, also used in lever action rifles, still would be loaded with pistol primers. Virtually all cartridges used solely in rifles do, however, use rifle primers.)
Primer chemistry
Primer manufacture and insertion is the most dangerous part of small arms ammunition production. Sensitive priming compounds have claimed many lives including the founder of the famous British EleyEley Brothers
Eley Brothers were a manufacturer of firearms cartridges at the Eley's Cartridge Factory, located in Edmonton and bordered by the River Lee Navigation and the Great Eastern Railway at Angel Road.- History :...
ammunition firm. Modern commercial operations use protective shielding between operators and manufacturing equipment.
Early primers used the same mercury fulminate used in 19th century percussion caps. Black powder could be effectively ignited by hot mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
released upon decomposition. Disadvantages of mercuric primers became evident with smokeless powder
Smokeless powder
Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...
loadings. Mercury fulminate slowly decomposed in storage until the remaining energy was insufficient for reliable ignition. Decreased ignition energy with age had not been recognized as a problem with black powder loadings because black powder could be ignited by as little energy as a static electricity discharge. Smokeless powder often required more thermal energy for ignition. Misfires and hang fire
Hang fire
Hang fire refers to an unexpected delay between the triggering of a firearm and the ignition of the propellant. This failure was common in firearm actions that relied on open primer pans, due to the poor or inconsistent quality of the powder. Modern weapons are susceptible, particularly if the...
s became common as the remaining priming compound sputtered in old primers. A misfire would result if the priming compound either failed to react to the firing pin fall or extinguished prior to igniting the powder charge. A hang fire is a perceptible delay between the fall of the firing pin and discharge of the firearm. In extreme cases, the delay might be sufficient to be interpreted as a misfire, and the cartridge could fire as the action was being opened or the firearm pointed in an inappropriate direction.
Incandescent particles were found most effective for igniting smokeless powder after the primary explosive gasses had heated the powder grains. Artillery charges frequently included a smaller quantity of black powder to be ignited by the primer, so incandescent potassium carbonate
Potassium carbonate
Potassium carbonate is a white salt, soluble in water , which forms a strongly alkaline solution. It can be made as the product of potassium hydroxide's absorbent reaction with carbon dioxide. It is deliquescent, often appearing a damp or wet solid...
would spread fire through the smokeless powder. Potassium chlorate
Potassium chlorate
Potassium chlorate is a compound containing potassium, chlorine and oxygen atoms, with the molecular formula KClO3. In its pure form, it is a white crystalline substance. It is the most common chlorate in industrial use...
was added to priming mixtures so incandescent potassium chloride
Potassium chloride
The chemical compound potassium chloride is a metal halide salt composed of potassium and chlorine. In its pure state, it is odorless and has a white or colorless vitreous crystal appearance, with a crystal structure that cleaves easily in three directions. Potassium chloride crystals are...
would have a similar effect in small arms cartridges.
Priming mixtures containing mercury fulminate leave metallic mercury in the bore and empty cartridge case after firing. The mercury was largely absorbed in the smokey fouling with black powder loads. Mercury coated the interior of brass
Brass
Brass is an alloy of copper and zinc; the proportions of zinc and copper can be varied to create a range of brasses with varying properties.In comparison, bronze is principally an alloy of copper and tin...
cases with smokeless powder loads, and the higher pressures of smokeless powder charges forced the mercury into grain boundaries between brass crystals where it formed zinc
Zinc
Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...
and copper
Copper
Copper is a chemical element with the symbol Cu and atomic number 29. It is a ductile metal with very high thermal and electrical conductivity. Pure copper is soft and malleable; an exposed surface has a reddish-orange tarnish...
amalgams
Amalgam (chemistry)
An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore.The...
weakening the case so it became unsuitable for reloading. The United States Army
United States Army
The United States Army is the main branch of the United States Armed Forces responsible for land-based military operations. It is the largest and oldest established branch of the U.S. military, and is one of seven U.S. uniformed services...
discontinued use of mercuric priming mixtures in 1898 to allow arsenal reloading of fired cases during peacetime. Frankford Arsenal
Frankford Arsenal
The Frankford Arsenal was a United States Army ammunition plant located adjacent to the Bridesburg neighborhood of Northeast Philadelphia, Pennsylvania, north of the original course of Frankford Creek.-History:...
primers used a mixture of potassium chlorate and antimony sulfide
Antimony sulfide
Antimony sulfide may refer to either of the following:*Stibnite, Sb2S3*Antimony pentasulfide, Sb2S5...
through the first half of the 20th century. These corrosive primers leave a residue of potassium chloride salt in the bore after a cartridge is fired. These hygroscopic salt crystals will hold moisture from a humid atmosphere and cause rusting. These corrosive primers can cause serious damage to the gun unless the barrel and action are cleaned carefully after firing.
Civilian ammunition manufacturers began offering non-corrosive primers in the 1920s, but most military ammunition continued to use corrosive priming mixtures of established reliability. The various proprietary priming formulations used by different manufacturers produced some significantly different ignition properties until the United States issued military specifications for non-corrosive lead styphnate
Lead styphnate
Lead styphnate , whose name is derived from styphnic acid, is an explosive used as a component in primer and detonator mixtures for less sensitive secondary explosives....
primers for 7.62x51mm NATO cartridge production. Most United States manufacturers adopted the military standard for their civilian production of Boxer primers. Manufacturers subsequently offered more powerful magnum primers for uniform ignition of civilian long-range or big-game cartridges with significantly greater powder capacity than required for standard infantry weapons.
Other explosives used in primers include lead azide, potassium perchlorate
Potassium perchlorate
Potassium perchlorate is the inorganic salt with the chemical formula KClO4. Like other perchlorates, this salt is a strong oxidizer and potentially reacts with many organic substances...
, or diazodinitrophenol (DDNP). New on the market in the late 1990s are lead-free primers, which address concerns over the lead and other heavy-metal compounds found in older primers. The heavy metals, while small in quantity, are released in the form of a very fine soot. Some indoor firing ranges are moving to ban primers containing heavy metals due to their toxicity. Lead-free primers were originally less sensitive and had a greater moisture sensitivity and correspondingly shorter shelf life than normal noncorrosive primers. Since their introduction, lead-free primers have become equal in performance to lead-based primers, and are gradually gaining popularity.
Military-surplus ammunition often uses inexpensive corrosive or slightly-corrosive Berdan primers because they work reliably under severe conditions, whereas modern Boxer primers are almost always non-corrosive and non-mercuric. Determination of corrosive or non-corrosive characteristics based on the primer type should consider these final headstamp
Headstamp
A headstamp is the markings on the bottom of a cartridge case designed for a firearm. It usually tells who manufactured the case. If it is a civilian case it often also tells the caliber, if it is military, the year of manufacture is often added....
dates of corrosive ammunition production:
- .45 ACP.45 ACPThe .45 ACP , also known as the .45 Auto by C.I.P., is a cartridge designed by John Browning in 1904, for use in his prototype Colt semi-automatic .45 pistol and eventually the M1911 pistol adopted by the United States Army in 1911.-Design and history:The U.S...
: FA 54, FCC 53, RA 52, TW 53, WCC 52, WRA 54 - .30-06 Springfield.30-06 SpringfieldThe .30-06 Springfield cartridge or 7.62×63mm in metric notation, was introduced to the United States Army in 1906 and standardized, and was in use until the 1960s and early 1970s. It replaced the .30-03, 6 mm Lee Navy, and .30 US Army...
: FA 56, LC 52, RA 51, SL 52, TW 52, WCC 51, WRA 54 - FN 57
Shotgun shells