A cartridge or a round is a type of pre-assembled firearm ammunition packaging a projectile (bullet, shots or slug), a propellant substance (usually either smokeless powder or black powder) and an ignition device (primer) within a metallic, paper or plastic case that is precisely made to fit within the barrel chamber of a breechloading gun, for the practical purpose of convenient transportation and handling during shooting. Although in popular usage the term "bullet" is often used to refer to a complete cartridge, it is correctly used only to refer to the projectile.
Cartridges can be categorized by the type of their primers--a small charge of an impact- or electric-sensitive chemical mixture that is located at the center of the case head (centerfire), inside the rim of the case base (rimfire and the now obsolete cupfire), in a sideway projection that is shaped like a pin (pinfire, now obsolete) or a lip (lipfire, now obsolete), or in a small nipple-like bulge at the case base (teat-fire, now obsolete).
Military and commercial producers continue to pursue the goal of caseless ammunition. Some artillery ammunition uses the same cartridge concept as found in small arms. In other cases, the artillery shell is separate from the propellant charge.
A cartridge without a projectile is called a blank. One that is completely inert (contains no active primer and no propellant) is called a dummy. One that failed to ignite and shoot off the projectile is called a dud, and one that ignited but failed to sufficiently push the projectile out of the barrel is called a squib.
The primary purpose is to be a handy all-in-one (projectile, right quantity of propellant, primer) for a shot. In modern, automatic weapons, it also provides the energy to move the parts of the gun which make it fire repeatedly. Many weapons were designed to make use of a readily available cartridge, or a new one with new qualities.
The cartridge case seals a firing chamber in all directions excepting the bore. A firing pin strikes the primer and ignites it. The primer compound deflagrates, it does not detonate (that is, it rapidly burns, but does not explode). A jet of burning gas from the primer ignites the propellant.
Gases from the burning powder pressurize and expand the case to seal it against the chamber wall. These propellant gases push on the bullet base. In response to this pressure, the bullet will move in the path of least resistance which is down the bore of the barrel. After the bullet leaves the barrel, the chamber pressure drops to atmospheric pressure. The case, which had been elastically expanded by chamber pressure, contracts slightly. This eases removal of the case from the chamber.
To manufacture cases for cartridges, a sheet of brass is punched into disks. These disks go through a series of drawing dies. The disks are annealed and washed before moving to the next series of dies. The brass needs to be annealed to remove the work-hardening in the material and make the brass malleable again ready for the next series of dies.
Manufacturing bullet jackets is similar to making brass cases: there is a series of drawing steps with annealing and washing.
Early primer was simply fine gunpowder poured into a pan or tube where it could be ignited by some external source of ignition such as a fuse or a spark. Modern primers are shock sensitive chemicals enclosed in a small (a few mm) capsule, ignited by percussion. In some instance ignition is electricity-primed, and there may even be no primer at all in such design (the propellant being directly ignited).
The case is commonly made of brass because it is resistant to corrosion. A brass case head can be work-hardened to withstand the high pressures of cartridges, and allow for manipulation via extraction and ejection without tearing the metal. The neck and body portion of a brass case is easily annealed to make the case ductile enough to allow reforming so that it can be reloaded many times.
Steel is used in some plinking ammunition, as well as in some military ammunition (mainly from the former Soviet Union and China). Steel is less expensive than brass, but it is not feasible to reload and reuse steel cases. Military forces typically consider small arms cartridge cases to be disposable, one-time-use devices.[according to whom?] However, case weight (mass) affects how much ammunition a soldier can carry, so the lighter steel cases do have a military advantage. Conversely, steel is more susceptible to contamination and damage so all such cases are varnished or otherwise sealed against the elements.
One downside caused by the increased strength of steel in the neck of these cases (compared to the annealed neck of a brass case) is that propellant gas can blow back past the neck and into the chamber. Constituents of these gases condense on the (relatively cold) chamber wall. This solid propellant residue can make extraction of fired cases difficult. This is less of a problem for small arms of the former Warsaw Pact nations, which were designed with much larger chamber tolerances than NATO weapons.
Aluminum cased cartridges are available commercially. These are generally not reloaded as aluminum fatigues easily during firing and resizing. Some calibers also have non-standard primer sizes to discourage reloaders from attempting to reuse these cases.
Historically paper had been used in the earliest cartridges.
Critical cartridge specifications include neck size, bullet weight and caliber, maximum pressure, headspace, overall length, case body diameter and taper, shoulder design, rim type, etc. Generally, every characteristic of a specific cartridge type is tightly controlled and few types are interchangeable in any way. Exceptions do exist but generally, these are only where a shorter cylindrical rimmed cartridge can be used in a longer chamber, (e.g., .22 Short in .22 Long Rifle chamber, and .38 Special in a .357 Magnum chamber). Centerfire primer type (Boxer or Berdan, see below) is interchangeable, although not in the same case. Deviation in any of these specifications can result in firearm damage and, in some instances, injury or death. Similarly, use of the wrong type of cartridge in any given gun can damage the gun, or cause bodily injury.
Cartridge specifications are determined by several standards organizations, including SAAMI in the United States, and C.I.P. in many European states. NATO also performs its own tests for military cartridges for its member nations; due to differences in testing methods, NATO cartridges (headstamped with the NATO cross) may present an unsafe combination when loaded into a weapon chambered for a cartridge certified by one of the other testing bodies.
Bullet diameter is measured either as a fraction of an inch (usually in 1/100 or in 1/1000) or in millimeters. Cartridge case length can also be designated in inches or millimeters.
Paper cartridges have been in use for nearly as long as hand-held firearms, with a number of sources dating their use back to the late 14th century. Historians note their use by soldiers of Christian I, Elector of Saxony and his son in the late 16th century, while the Dresden Armoury has evidence dating their use to 1591. Capo Bianco wrote in 1597 that paper cartridges had long been in use by Neapolitan soldiers. Their use became widespread by the 17th century. The 1586 cartridge consisted of a charge of powder and a bullet in a paper tube. Thick paper is still known as "cartridge paper" from its use in these cartridges. Another source states the cartridge appeared in 1590. King Gustavus Adolphus of Sweden had his troops use cartridges in the 1600s. The paper was formed a cylinder with twisted ends; the ball was at one end, and the measured powder filled the rest.
This cartridge was used with muzzle-loading military firearms, probably more often than for sporting shooting, the base of the cartridge being ripped or bitten off by the soldier, the powder poured into the barrel, and the paper and bullet rammed down the barrel. In the Civil War era cartridge, the paper was supposed to be discarded, but soldiers often used it as a wad. To ignite the charge an additional step was required where a finer-grained powder called priming powder was poured into the pan of the gun to be ignited by the firing mechanism.
The evolving nature of warfare required a firearm that could load and fire more rapidly, resulting in the flintlock musket (and later the Baker rifle), in which the pan was covered by furrowed steel. This was struck by the flint and fired the gun. In the course of loading a pinch of powder from the cartridge would be placed into the pan as priming, before the rest of the cartridge was rammed down the barrel, providing charge and wadding.
Later developments rendered this method of priming unnecessary, as, in loading, a portion of the charge of powder passed from the barrel through the vent into the pan, where it was held by the cover and hammer.
The next important advance in the method of ignition was the introduction of the copper percussion cap. This was only generally applied to the British military musket (the Brown Bess) in 1842, a quarter of a century after the invention of percussion powder and after an elaborate government test at Woolwich in 1834. The invention that made the percussion cap possible was patented by the Rev. A. J. Forsyth in 1807, and consisted of priming with a fulminating powder made of potassium chlorate, sulfur, and charcoal, which ignited by concussion. This invention was gradually developed, and used, first in a steel cap, and then in a copper cap, by various gunmakers and private individuals before coming into general military use nearly thirty years later.
The alteration of the military flint-lock to the percussion musket was easily accomplished by replacing the powder pan with a perforated nipple, and by replacing the cock or hammer that held the flint with a smaller hammer that had a hollow to fit on the nipple when released by the trigger. The shooter placed a percussion cap (now made of three parts of potassium chlorate, two of fulminate of mercury and powdered glass) on the nipple. The detonating cap thus invented and adopted brought about the invention of the modern cartridge case, and rendered possible the general adoption of the breech-loading principle for all varieties of rifles, shotguns and pistols. This greatly streamlined the reloading procedure and paved the way for semi- and full-automatic firearms.
However, this big leap forward came at a price. It introduced an extra component into each round -- the cartridge case -- which had to be removed before the gun could be reloaded. While a flintlock, for example, is immediately ready to reload once it has been fired, adopting brass cartridge cases brought in the problems of extraction and ejection. The mechanism of a modern gun not only must load and fire the piece but also must remove the spent case, which might require just as many added moving parts. Many malfunctions involve this process, either through failure to extract a case properly from the chamber or by allowing the extracted case to jam the action. Nineteenth-century inventors were reluctant to accept this added complication and experimented with a variety of caseless or self-consuming cartridges before finally accepting that the advantages of brass cases far outweighed this one drawback.
The first integrated cartridge was developed in Paris in 1808 by the Swiss gunsmith Jean Samuel Pauly in association with French gunsmith François Prélat. Pauly created the first fully self-contained cartridges: the cartridges incorporated a copper base with integrated mercury fulminate primer powder (the major innovation of Pauly), a round bullet and either brass or paper casing. The cartridge was loaded through the breech and fired with a needle. The needle-activated centerfire breech-loading gun would become a major feature of firearms thereafter. Pauly made an improved version, protected by a patent, on 29 September 1812.
Probably no invention connected with firearms has wrought such changes in the principle of gun construction as those effected by the "expansive cartridge case." This invention has completely revolutionized the art of gun making, has been successfully applied to all descriptions of firearms, and has produced a new and important industry: that of cartridge manufacture. Its essential feature is preventing gas escaping the breech when the gun is fired, by means of an expansive cartridge case containing its own means of ignition. Previous to this invention shotguns and sporting rifles were loaded by means of powder flasks and shot bags or flasks, bullets, wads and copper caps, all carried separately. One of the earliest efficient modern cartridge cases was the pinfire cartridge, developed by French gunsmith Casimir Lefaucheux in 1836. It consisted of a thin weak shell made of brass and paper that expanded from the force of the explosion. This fit perfectly in the barrel, and thus formed an efficient gas check. A small percussion cap was placed in the middle of the base of the cartridge, and was ignited by means of a brass pin projecting from the side and struck by the hammer. This pin also afforded the means of extracting the cartridge case. This cartridge was introduced in England by Lang, of Cockspur Street, London, about 1845.
In the American Civil War (1861-65) a breech-loading rifle, the Sharps, was introduced and produced in large numbers. It could be loaded with either a ball or a paper cartridge. After that war many were converted to the use of metal cartridges. The development by Smith & Wesson (amongst many others) of revolver handguns that used metal cartridges helped to establish cartridge firearms as the standard in the US by the late 1860s and early 1870s, although many continue to use percussion revolvers well after that.
The first pinfire metallic cartridge metallic cartridge was invented by Jean Samuel Pauly in the first decades of the 19th century. However, it bore little resemblance to the modern rimfire and centerfire cartridges which would be invented in the mid- to late-19th century.
Frenchman Louis-Nicolas Flobert invented the first rimfire metallic cartridge in 1845. His cartridge consisted of a percussion cap with a bullet attached to the top. Flobert then made what he called "parlor guns" for this cartridge, as these rifles and pistols were designed to be shot in indoor shooting parlors in large homes. These 6mm Flobert cartridges, do not contain any powder, the only propellant substance contained in the cartridge is the percussion cap. In English-speaking countries, the 6mm Flobert cartridge corresponds to .22 BB Cap and .22 CB Cap ammunition. These cartridges have a relatively low muzzle velocity of around 700 ft/s (210 m/s).
French gunsmith Benjamin Houllier improved the Lefaucheux pinfire cardboard cartridge and patented in Paris in 1846, the first fully metallic pinfire cartridge containing powder (and a pinfire), in a metallic cartridge. He also included in his patent claims rim and centerfire primed cartridges using brass or copper casings. Houllier commercialised his weapons in association with the gunsmiths Blanchard or Charles Robert.
In the United States, in 1857, the Flobert cartridge inspired the .22 Short (another rimfire), especially conceived for the first American revolver using rimfire cartridges, the Smith & Wesson Model 1. A year before, in 1856, the LeMat was the first American (French-designed) breech-loading revolver, but it used pinfire cartridges, not rimfire. Formerly, an employee of the Colt's Patent Firearms Manufacturing Company, Rollin White, had been the first in America to conceive the idea of having the revolver cylinder bored through to accept metallic cartridges (circa 1852), with the first in the world to use bored-through cylinders probably having been Lefaucheux in 1845, who invented a pepperbox-revolver loaded from the rear using bored-through cylinders. However, Samuel Colt refused this innovation. White left Colt, went to Smith & Wesson to rent a licence for his patent, and this is how the S&W Model 1 saw light of day in 1857. The patent didn't definitely expire until 1870, allowing Smith & Wesson competitors to design and commercialise their own revolving breech-loaders using metallic cartridges. Famous models of that time are the Colts Open Top (1871-1872) and Single Action Army "Peacemaker" (1873). But in rifles, the lever-action mechanism patents were not obstructed by Rollin White's patent infringement because White only held a patent concerning drilled cylinders and revolving mechanisms. Thus, larger caliber rimfire cartridges were soon introduced after 1857, when the Smith & Wesson .22 Short ammunition was introduced for the first time. Some of these rifle cartridges were used in the American Civil War, including the .44 Henry and 56-56 Spencer (both in 1860). However, the large rimfire cartridges were soon replaced by centerfire cartridges, which could safely handle higher pressures.
In 1867 the British war office adopted the Eley-Boxer metallic centerfire cartridge case in the Pattern 1853 Enfield rifles, which were converted to Snider-Enfield breech-loaders on the Snider principle. This consisted of a block opening on a hinge, thus forming a false breech against which the cartridge rested. The priming cap was in the base of the cartridge, and was discharged by a striker passing through the breech block. Other European powers adopted breech-loading military rifles from 1866 to 1868, with paper instead of metallic cartridge cases. The original Eley-Boxer cartridge case was made of thin-coiled brass--occasionally these cartridges could break apart and jam the breech with the unwound remains of the case upon firing. Later the solid-drawn, centerfire cartridge case, made of one entire solid piece of tough hard metal, an alloy of copper, with a solid head of thicker metal, has been generally substituted.
Around 1870, machined tolerances had improved to the point that the cartridge case was no longer necessary to seal a firing chamber. Precision-faced bolts would seal as well, and could be economically manufactured. However, normal wear and tear proved this system to be generally infeasible.
The name of any given cartridge does not necessarily reflect any cartridge or gun dimension. The name is merely the standardized and accepted moniker. SAAMI (Sporting Arms and Ammunition Manufacturers' Institute) and the European counterpart (CIP) and members of those organizations specify correct cartridge names. Cartridge names, when correctly presented, never include a naked leading decimal point.
It is a common misnomer to refer to a cartridge as a certain "caliber," e.g. "30-06 caliber." The correct full name for this cartridge is .30-'06 Springfield. The "-'06" means it was introduced in 1906. In sporting arms the only consistent definition of "caliber" is bore diameter. Dozens of unique .30-caliber cartridge types exist.
There is considerable variation in cartridge nomenclature. Names sometimes reflect various characteristics of the cartridge. For example, the .308 Winchester uses a bullet of 308/1000-inch diameter and was standardized by Winchester. Conversely, cartridge names often reflect nothing related to the cartridge in any obvious way. For example, the .218 Bee uses a bullet of 224/1000-inch diameter, fired through a .22-in bore, etc. The 218 and Bee portions of this cartridge name reflect nothing other than the desires of those who standardized that cartridge. Many similar examples exist, for example: .219 Zipper, .221 Fireball, .222 Remington, .256 Winchester, .280 Remington, .307 Winchester, .356 Winchester.
Where two numbers are used in a cartridge name, the second number may reflect a variety of things. Frequently the first number reflects bore diameter (inches or millimeters). The second number reflects case length (in inches or mm). For example, the 7.62×51mm NATO refers to a bore diameter of 7.62 mm and has an overall case length of 51 mm. The commercial version is the .308 Winchester.)
In older black powder cartridges, the second number typically refers to powder charge, in grains. For example, the .50-90 Sharps has a .50-inch bore and used a nominal charge of 90.0 grains (5.83 g) of black powder.
Many such cartridges were designated by a three-number system, e.g., 45-120-3¼ Sharps: 45-caliber bore, 120 grains of (black) powder, 3¼-inch long case. Other times a similar three-number system indicated bore (caliber), charge (grains), and bullet weight (grains). The 45-70-500 Government is an example.
Often, the name reflects the company or individual who standardized it, such as the .30 Newton, or some characteristic important to that person.
The .38 Special actually has a nominal bullet diameter of 0.3570 inches (9.07 mm) (jacketed) or 0.3580 inches (9.09 mm) (lead) while the case has a nominal diameter of 0.3800 inches (9.65 mm),. Hence the name. This is historically logical. The hole drilled through the chambers of .36-caliber cap-and-ball revolvers when converting those to work with cartridges was 0.3800 inches (9.65 mm) and the cartridges made to work in those revolvers was logically named the .38 Colt. The original cartridges used a heeled bullet like a .22 rimfire where the bullet was the same diameter as the case. Early Colt Army .38s have a bore diameter that will allow a .357" diameter bullet to slide through the barrel. The cylinder is bored straight through with no step. Later versions used an inside the case lubricated bullet of .357" diameter instead of the original .38" with a reduction in bore diameter. The difference in .38 Special bullet diameter and case diameter reflects the thickness of the case mouth (approximately 11/1000-inch per side). The .357 Magnum evolved from the .38 Special. The .357 was named to reflect bullet diameter (in thousandths inch), not case diameter. "Magnum" was used to indicate its longer case and higher operating pressure.
Cartridges are classified by some major characteristics. One classification is the location of the primer. Early cartridges began with the pinfire, then the rimfire, and finally the centerfire.
Another classification describes how cartridges are located in the chamber (headspace). Rimmed cartridges are located with the rim near the cartridge head; the rim is also used to extract the cartridge from the chamber. Examples are the .22 long rifle and .303 British. In a rimless cartridge, the cartridge head diameter is about the same as or smaller than the body diameter. The head will have a groove so the cartridge can be extracted from the chamber. Locating the cartridge in the chamber is accomplished by other means. Some rimless cartridges are necked down, and they are positioned by the cartridge's shoulder. An example is the .30-06 Springfield. Pistol cartridges may be located by the end of the brass case. An example is the .45 ACP. A belted cartridge has a larger diameter band of thick metal near the head of the cartridge. An example is the .300 Weatherby Magnum. An extreme version of the rimless cartridge is the rebated case; guns employing advanced primer ignition need such a case because the case moves during firing (i.e., it is not located at a fixed position). An example is the 20mm×110RB.
A centerfire cartridge has a centrally located primer held within a recess in the case head. Most centerfire brass cases used worldwide for sporting ammunition use Boxer primers. It is easy to remove and replace Boxer primers using standard reloading tools, facilitating reuse.
Some European- and Asian-manufactured military and sporting ammunition uses Berdan primers. Removing the spent primer from (decapping) these cases requires use of a special tool because the primer anvil (on which the primer compound is crushed) is an integral part of the case and the case therefore does not have a central hole through which a decapping tool can push the primer out from the inside, as is done with Boxer primers. In Berdan cases, the flash holes are located to the sides of the anvil. With the right tool and components, reloading Berdan-primed cases is perfectly feasible. However, Berdan primers are not readily available in the U.S.
Rimfire priming was a popular solution before centerfire priming was perfected. In a rimfire case, centrifugal force pushes a liquid priming compound into the internal recess of the folded rim as the manufacturer spins the case at a high rate and heats the spinning case to dry the priming compound mixture in place within the hollow cavity formed within the rim fold at the perimeter of the case interior.
In the mid- to late-1800s, many rimfire cartridge designs existed. Today only a few, mostly for use in small-caliber guns, remain in general and widespread use. These include the .17 Mach II, .17 Hornady Magnum Rimfire (HMR), 5mm Remington Magnum (Rem Mag), .22 (BB, CB, Short, Long, Long Rifle), and .22 Winchester Magnum Rimfire (WMR).
Compared to modern centerfire cases used in the strongest types of modern guns, existing rimfire cartridge designs use loads that generate relatively low pressure because of limitations of feasible gun design -- the rim has little or no lateral support from the gun. Such support would require very close tolerances in design of the chamber, bolt, and firing pin. Because that is not cost-effective, it is necessary to keep rimfire load pressure low enough so that the stress generated by chamber pressure that would push the case rim outward cannot expand the rim significantly. Also, the wall of the folded rim must be thin and ductile enough to easily deform, as necessary to allow the blow from the firing pin to crush and thereby ignite the primer compound, and it must do so without rupturing, If it is too thick, it will be too resistant to deformation. If it is too hard, it will crack rather than deform. These two limitations -- that the rim is self-supporting laterally and that the rim is thin and ductile enough to easily crush in response to the firing pin impact -- limit rimfire pressures.
Modern centerfire cartridges are often loaded to about 65,000 psi (450,000 kPa) maximum chamber pressure. Conversely, no commercialized rimfire has ever been loaded above about 40,000 psi (280,000 kPa) maximum chamber pressure. However, with careful gun design and production, no fundamental reason exists that higher pressures could not be used. Despite the relative pressure disadvantage, modern rimfire magnums in .17-caliber, 5mm, and .22-caliber generate muzzle energy comparable to smaller centerfire cartridges.
Today, .22 LR (Long Rifle) accounts for the vast majority of all rimfire ammunition used. Standard .22 LR rounds use an essentially pure lead bullet plated with a typical 95% copper, 5% zinc combination. These are offered in supersonic and subsonic types, as well as target, plinking, and hunting versions. These cartridges are usually coated with a hard wax for fouling control.
The .22 LR and related rimfire .22 cartridges use a heeled bullet, where external diameter of the case is the same as diameter of the forward portion of the bullet and where the rearward portion of the bullet, which extends into the case, is necessarily smaller in diameter than the main body of the bullet.
Most revolver cartridges have a rim at the base of the case that is larger than the case body is and which seats against or into the cylinder block to provide headspace control (to keep the cartridge from moving too far forward in the cylinder chamber) and to provide for easy extraction.
Nearly every semi-automatic pistol cartridge is "rimless," or more precisely has a rim of the same diameter as the case body. An extractor engages this rim by entering a cannelure near the base of the case. A few designs, known as "semi-rimmed" have a rim that is slightly larger than case body diameter but these function as a rimless design. All such cartridges headspace on the case mouth (although some, such as .38 Super, at one time seated on the rim, this was changed for accuracy reasons), which prevents the round from entering too far into the chamber. Some cartridges have a rim that is significantly smaller than case body diameter. These are known as rebated-rim designs, and almost always allow a handgun to fire multiple caliber cartridges with only a barrel and magazine change.
The Hague Convention of 1899 bans the use of expanding projectiles against the military forces of other nations. Some countries accept this as a blanket ban against the use of expanding projectiles against anyone, while others[note 1] use JSP and HP against non-military forces such as terrorists and criminals.
Ammunition types are listed numerically.
Snake shot (AKA: bird shot, rat shot and dust shot) refers to handgun and rifle cartridges loaded with small lead shot. Snake shot is generally used for shooting at snakes, rodents, birds, and other pests at very close range.
The most common snake shot cartridge is .22 Long Rifle loaded with #12 shot. From a standard rifle these can produce effective patterns only to a distance of about 3 metres (10 ft) - but in a smoothbore shotgun this can extend as far as 15 metres (50 ft).
Many governments and companies continue to develop caseless ammunition (where the entire case assembly is either consumed when the round fires or whatever remains is ejected with the bullet). So far, none of these have been successful enough to reach the civilian market and gain commercial success. Even within the military market, use is limited. Around 1848, Sharps introduced a rifle and paper cartridge (containing everything but the primer) system. When new these guns had significant gas leaks at the chamber end, and with use these leaks progressively worsened. This problem plagues caseless cartridge and gun systems to this day.
The Daisy Heddon VL Single Shot Rifle, which used a caseless round in .22 caliber, was produced by the air gun company, beginning in 1968. Apparently Daisy never considered the gun an actual firearm. In 1969, the ATF ruled it was in fact a firearm, which Daisy was not licensed to produce. Production of the guns and the ammo was discontinued in 1969. They are still available on the secondary market, mainly as collector items, as most owners report that accuracy is not very good.
In 1989, Heckler & Koch, a prominent German firearms manufacturer, began advertising the G11 assault rifle, which shot a 4.73×33 square caseless round. The round was mechanically fired, with an integral primer.
In 1993 Voere of Austria began selling a gun and caseless ammunition. Their system used a primer, electronically fired at 17.5 ± 2 volts. The upper and lower limits prevent fire from either stray currents or static electricity. The direct electrical firing eliminates the mechanical delays associated with a striker, reducing lock time, and allowing for easier adjustment of the rifle trigger.
In both instances, the "case" was molded directly from solid nitrocellulose, which is itself relatively strong and inert. The bullet and primer were glued into the propellant block.
The "Tround" ("Triangular Round") was a unique type of cartridge designed in 1958 by David Dardick, for use in specially designed Dardick 1100 and Dardick 1500 open-chamber firearms. As their name suggests, Trounds were triangular in cross-section, and were made of plastic or aluminum, with the cartridge completely encasing the powder and projectile. The Tround design was also produced as a cartridge adaptor, to allow conventional .38 Special and 22 Long Rifle cartridges to be used with the Dardick firearms.
A blank is a charged cartridge that does not contain a projectile, alternatively uses a non-metallic (for instance wooden) projectile that pulverizes when hitting a blank firing adapter. To contain the propellant, the opening where the projectile would normally be located is crimped shut and or it is sealed with some material that disperses rapidly upon leaving the barrel.
This sealing material can still potentially cause harm at extremely close range. Actor Jon-Erik Hexum died when he shot himself in the head with a blank, and actor Brandon Lee was famously killed during filming of The Crow when a blank fired behind a bullet that was stuck in the bore drove that bullet through his abdomen and into his spine. The gun had not been properly deactivated and a primed case with a bullet instead of a dummy had been used previously. Someone pulled the trigger and the primer drove the bullet silently into the bore.
Blanks are used in training, but do not always cause a gun to behave the same as live ammunition does; recoil is always far weaker, and some automatic guns only cycle correctly when the gun is fitted with a blank-firing adaptor to confine gas pressure within the barrel to operate the gas system.
Blanks can also be used to launch a rifle grenade, although later systems used a "bullet trap" design that captures a bullet from a conventional round, speeding deployment. This also negates the risk of mistakenly firing a live bullet into the rifle grenade, causing it to instantly explode instead of propelling it forward.
The power loads used in a variety of nail guns are essentially rimfire blanks.
Drill rounds are inert versions of cartridges used for education and practice during military training. Other than the lack of propellant and primer, these are the same size as normal cartridges and will fit into the mechanism of a gun in the same way as a live cartridge does. Because dry-firing (releasing the firing pin with an empty chamber) a gun can sometimes lead to firing pin (striker) damage, dummy rounds termed snap caps are designed to protect centerfire guns from possible damage during "dry-fire" trigger control practices.
To distinguish drill rounds and snap-caps from live rounds these are marked distinctively. Several forms of markings are used; e.g. setting colored flutes in the case, drilling holes through the case, coloring the bullet or cartridge, or a combination of these. In the case of centerfire drill rounds the primer will often be absent, its mounting hole in the base is left open. Because these are mechanically identical to live rounds, which are intended to be loaded once, fired and then discarded, drill rounds have a tendency to become significantly worn and damaged with repeated passage through magazines and firing mechanisms, and must be frequently inspected to ensure that these are not so degraded as to be unusable--for example the cases can become torn or misshapen and snag on moving parts, or the bullet can become separated and stay in the breech when the case is ejected.
The bright-colored Mek-Porek is an inert cartridge base designed to prevent a live round from being unintentionally chambered, to reduce the chances of an accidental discharge from mechanical or operator failure. An L-shaped flag is visible from the outside, so that the shooter and other people concerned are instantly aware about the situation of the weapon. The Mek-Porek is usually tethered to its weapon by a short string, and can be quickly ejected to make way for a live round if the situation suddenly warrants. This safety device is standard-issue in the Israel Defense Forces.
A snap cap is a device which is shaped like a standard cartridge but contains no primer, propellant or projectile. It is used to ensure that dry firing firearms of certain designs does not cause damage. A small number of rimfire and centerfire firearms of older design should not be test-fired with the chamber empty, as this can lead to weakening or breakage of the firing pin and increased wear to other components in those firearms. In the instance of a rimfire weapon of primitive design, dry firing can also cause deformation of the chamber edge. For this reason some shooters use a snap cap in an attempt to cushion the weapon's firing pin as it moves forward. Some snap caps contain a spring-dampened fake primer, or one made of plastic, or none at all; the springs or plastic absorb force from the firing pin, allowing the user to safely test the function of the firearm action without damaging its components.
Snap caps and action-proving dummy cartridges also work as a training tool to replace live rounds for loading and unloading drills, as well as training for misfires or other malfunctions, as they function identically to a live "dud" round that has not ignited. Usually one snap-cap is usable for 300 to 400 clicks. After that, due to the hole at the false primer, the firing pin does not reach it.
The rimfire cartridge, which was used so successfully in the Henry and the Model 66, was limited to relatively weak loads of powder and comparatively lightweight bullets. These limitations, which still apply, came from the construction of the rimfire cartridge and from the action of the priming mixture. Rimfire cartridges must be made of thin metal or the firing pin cannot indent the head and explode the primer. This thin-walled cartridge case limits the pressure developed by the powder charge and consequently the weight of the bullet. If too much powder is used, there is a danger that the cartridge case will burst at the folded rim when it is fired, and that the primer flash, passing laterally across the rear of the powder charge, will not ignite a large load sufficiently to consume all of the powder before the bullet leaves the cartridge case. These limitations were overcome with the development of the centerfire cartridge....