Cartridge (firearms)

A cartridge,^[1]^[2] also known as a round, is a type of pre-assembled firearm ammunition packaging a projectile (bullet, shot, or slug), a propellant substance (smokeless powder, black powder substitute, 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 convenient transportation and handling during shooting.^[3] Although in popular usage the term "bullet" is often used to refer to a complete cartridge, the correct usage only refers to the projectile.

Cartridges can be categorized by the type of primer. This can be accomplished by igniting a small charge of an impact-sensitive explosive compound or by an electric-sensitive chemical mixture that is located: at the center of the case head (centerfire); or inside the rim (rimfire); or inside the walls on the fold of the case base that is shaped like a cup (cupfire); or in a sideways projection that is shaped like a pin (pinfire) or a lip (lipfire); or in a small bulge shaped like a nipple at the case base (teatfire). Only small-caliber rimfire cartridges and centerfire cartridges have survived into the modern day.

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.

Design[edit]

Purpose[edit]

The cartridge was invented specifically for breechloading firearms. Prior to its invention, the projectiles and propellant were carried separately and had to be individually loaded via the muzzle into the gun barrel before firing, then have a separate ignitor compound (from a burning slow match, to a small charge of gunpowder in a flash pan, to a metallic percussion cap mounted on top of a "nipple" or cone), to serve as a source of activation energy to set off the shot. Such loading procedures often require adding paper/cloth wadding and ramming down repeatedly with a rod to optimize the gas seal, and are thus clumsy and inconvenient, severely restricting the practical rate of fire of the weapon, leaving the shooter vulnerable to the threat of close combat (particularly cavalry charges) as well as complicating the logistics of ammunition.

The primary purpose of using a cartridge is to offer a handy pre-assembled "all-in-one" package that is convenient to handle and transport, easily loaded into the breech (rear end) of the barrel, as well as preventing potential propellant loss, contamination or degradation from moisture and the elements. In modern self-loading firearms, the cartridge case also enables the action mechanism to use part of the propellant's energy (carried inside the cartridge itself) and cyclically load new rounds of ammunition to allow quick repeated firing.

To perform a firing, the round is first inserted into a "ready" position within the chamber aligned with the bore axis (i.e. "in battery"). While in the chamber, the cartridge case obturates all other directions except the bore to the front, reinforced by a breechblock or a locked bolt from behind, designating the forward direction as the path of least resistance. When the trigger is pulled, the sear disengages and releases the hammer/striker, causing the firing pin to impact the primer embedded in the base of the cartridge. The shock-sensitive chemical in the primer then creates a jet of sparks that travels into the case and ignites the main propellant charge within, causing the powders to deflagrate (but not detonate). This rapid exothermic combustion yields a mixture of highly energetic gases and generates a very high pressure inside the case, often fire-forming it against the chamber wall. When the pressure builds up sufficiently to overcome the fastening friction between the projectile (e.g. bullet) and the case neck, the projectile will detach from the case and, pushed by the expanding high-pressure gases behind it, move down the bore and out the muzzle at extremely high speed. After the bullet exits the barrel, the gases are released to the surroundings as ejectae in a loud blast, and the chamber pressure drops back down to ambient level. The case, which had been elastically expanded by high pressure, contracts slightly, which eases its removal from the chamber when pulled by the extractor. The spent cartridge, with its projectile and propellant gone but the case still containing a used-up primer, then gets ejected from the gun to clear room for a subsequent new round.

Components[edit]

A modern cartridge consists of four main components: the case, the projectile, the propellant, and the primer.

Nomenclature[edit]

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.

It is incomplete to refer to a cartridge as a certain "caliber" (e.g., "30-06 caliber"), as the word caliber only describes the bullet diameter. The correct full name for this round is .30–'06 Springfield. The "-'06" means it was introduced in 1906. In sporting arms, the only consistent definition of "caliber" is bore diameter, and dozens of unique .30-caliber round 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, with a total length of 71.1 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., 45–120–31⁄4 Sharps: 45-caliber bore, 120 grains of (black) powder, 31⁄4-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 cartridge 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.

Rimless .380 ACP semi-automatic cartridge

Rimmed .38 special revolver cartridge

Most revolver cartridges are rimmed at the base of the case, which seats against the edge of the cylinder chamber to provide headspace control (to keep the cartridge from moving too far forward into the chamber) and to facilitate easy extraction.

Nearly every centerfire semi-automatic pistol cartridge is "rimless", where the rim is of the same diameter as the case body but separated by a circumferential groove in between, into which the extractor engages the rim by hooking. A "semi-rimmed" cartridge is essentially a rimless one but the rim diameter is slightly larger than the case body, and a "rebated rimless" cartridge is one with the rim smaller in diameter. 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 the 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.

A loaded with multiple metallic "shot", which are small, generally spherical projectiles.

shotgun shell

: A single solid projectile designed to be fired from a shotgun.

Shotgun slug

: a generally non-lethal projectile fired from a riot gun.

Baton round

Armor-piercing

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.^[49]

(22 LR): A round that is often used for target shooting and the hunting of small game such as squirrels. Because of the small size of this round, the smallest self-defense handguns chambered in 22 rimfire (though less effective than most centerfire handguns cartridges) can be concealed in situations where a handgun chambered for a centerfire cartridge could not. The 22 LR is the most commonly fired sporting arms cartridge, primarily because, when compared to any centerfire ammunition, 22 LR ammunition is much less expensive and because recoil generated by the light 22 bullet at modest velocity is very mild.

22 Long Rifle

: A very popular round for medium to long range small game and varmint hunting, pest control, and target shooting. The 22–250 is one of the most popular rounds for fox hunting and other pest control in Western Europe due to its flat trajectory and very good accuracy on rabbit to fox-sized pests.

.22-250 Remington

: One of the most popular big game hunting rounds of all time. Also, as a long-range sniping round, it is favored by US Navy SEALs and the German Bundeswehr. While not in the same class as the 338 Lapua, it has roughly the same power as 7 mm Remington Magnum, and easily exceeds the performance of 7.62×51mm NATO.

.300 Winchester Magnum

(7.62×63mm): The standard US Army rifle round for the first half of the 20th century. It is a full-power rifle round suitable for hunting most North American game and most big game worldwide.^[50]

30-06 Springfield

: the standard British Empire military rifle cartridge from 1888 to 1954.^[51]

.303 British

: the commercial name of a centerfire cartridge based on the military 7.62×51mm NATO round. Two years prior to the NATO adoption of the 7.62×51mm NATO T65 in 1954, Winchester (a subsidiary of the Olin Corporation) branded the round and introduced it to the commercial hunting market as the 308 Winchester. The Winchester Model 70 and Model 88 rifles were subsequently chambered for this round. Since then, the 308 Winchester has become the most popular short-action big-game hunting round worldwide. It is also commonly used for civilian and military target events, military sniping, and police sharpshooting.

.308 Winchester

: Using a lengthened version of the .38 Special case that was loaded to about twice the maximum chamber pressure of the.38 Special and was rapidly acceptedfor use by hunters and law enforcement officers. At the time of its introduction, 357 Magnum bullets were claimed to easily pierce the steel body panels of automobiles and crack engine blocks (to disable the vehicle).^[52]

.357 Magnum

: designed for hunting African big game in the early 20th century and legislated as the minimum diameter rifle caliber for African big game hunting during the mid-20th century^[53]

.375 Holland & Holland Magnum

: A shorter-cased version of the 10mm Auto.

.40 S&W

: A high-powered pistol round designed primarily for hunting.

.44 Magnum

: The standard US pistol round for about one century. Typical 45 ACP loads are subsonic.^[54]

.45 ACP

: a more powerful 45-caliber revolver round using a longer cartridge. The 45 Colt was designed for the Colt Single Action Army and adopted by the US Army in 1873. Other 45-caliber single-action and double-action revolvers also use this round.

.45 Colt

: Adopted by the US Army in 1873 as their standard service rifle cartridge for the Springfield Model 1873 rifle. Most commercial loadings of this cartridge are constrained by the possibility that someone might attempt to fire a modern loading in a vintage rifle or replica. However, current production rifles from Marlin, Ruger, and Browning can accept loads that generate nearly twice the pressure generated by the original black powder cartridges.

.45-70 Government

(12.7×99mm NATO): Originally designed to destroy aircraft in the First World War,^[55] this round still serves an anti-materiel round against light armor. It is used in heavy machine guns and high-powered sniper rifles. Such rifles can be used, amongst other things, for destroying military matériel such as sensitive parts of grounded aircraft and armored transports. Civilian shooters use these for long-distance target shooting.

.50 BMG

Soviet: The Soviet response to the 5.56×45mm NATO round.

5.45×39mm

: Adopted by the US military in the 1960s, it later became the NATO standard rifle round in the early 1980s, displacing the 7.62×51mm. Remington later adopted this military round as the .223 Remington, a very popular round for varminting and small game hunting.

5.56×45mm NATO

: One of the most popular long range varmint and medium- to big-game hunting rounds in Europe, especially in the countries such as France and (formerly) Belgium where the possession of firearms chambered for a (former) military round is forbidden or is more heavily restricted. This round is offered by European rifle makers in both bolt-action rifles and a rimmed version. The 7×65mmR is chambered in double and combination rifles. Another reason for its popularity is its flat trajectory, very good penetration, and high versatility, depending on what bullet and load are used. Combined with a large choice of different 7 mm bullets available the 7×64mm is used on everything from fox and geese to red deer, Scandinavian moose and European brown bear equivalent to the North American black bear. The 7×64mm essentially duplicates the performance of the 270 Winchester and 280 Remington.

7×64mm

: A long-range hunting round.

7 mm Remington Magnum

: The standard Soviet/ComBloc rifle round from the mid-1940s to the mid-1970s, this is easily one of the most widely distributed rounds in the world due to the distribution of the ubiquitous Kalashnikov AK-47 series.

7.62×39mm

: This was the standard NATO rifle round until its replacement by the 5.56×45mm. It is currently the standard NATO sniper rifle and medium machinegun chambering. In the 1950s, it was the standard NATO round for rifles, but recoil and weight proved problematic for the new battle rifle designs such as the FN FAL. Standardized commercially as the 308 Winchester.

7.62×51mm NATO

: The standard Russian rifle round from the 1890s to the mid-1940s. The "R" stands for rimmed. The 7.62×54mmR rifle round is a Russian design dating back to 1891. Originally designed for the Mosin-Nagant rifle, it was used during the late Tsarist era and throughout the Soviet period, in machine guns and rifles such as the SVT-40. The Winchester Model 1895 was also chambered for this cartridge per contract with the Russian government. It is still in use by the Russian military in the Dragunov and other sniper rifles and some machine guns. The round is colloquially known as the "7.62 Russian". This name sometimes causes people to confuse this round with the "7.62 Soviet" round, which refers to the 7.62 × 39 round used in the SKS and AK-47 rifles.

7.62×54mmR

(32 ACP): A very small pistol round. However, this was the predominant Police Service round in Europe until the mid-1970s. The "SR" stands for semi-rimmed, meaning the case rim is slightly larger than the case body diameter.

7.65×17mm Browning SR

: The standard German service rifle round from 1888 to 1945, the 8×57mmIS (aka 8 mm Mauser) has seen wide distribution around the globe through commercial, surplus, and military sales, and is still a popular and commonly used hunting round in most of Europe, partly because of the abundance of affordable hunting rifles in this chambering as well as a broad availability of different hunting, target, and military surplus ammunition available.^[56]

8×57mm IS

: Invented for the German military at the turn of the 20th century, the wide distribution of the 9×19mm Parabellum round made it the logical choice for the NATO standard pistol and Submachine gun round.

9×19mm Parabellum

: Very common big game hunting round in Scandinavia along with the 6.5×55mm, where it is used as a very versatile hunting round on anything from small and medium game with lightweight cast lead bullets to the largest European big game with heavy soft point hunting bullets. The 9.3×62mm is also very popular in the rest of Europe for Big game, especially driven Big game hunts due to its effective stopping power on running game. And, it is the single round smaller than the 375 H&H Magnum that has routinely been allowed for legal hunting of dangerous African species.

9.3×62mm

: The 12.7×108mm round is a heavy machine gun and anti-materiel rifle round used by the Soviet Union, the former Warsaw Pact, modern Russia, and other countries. It is the approximate Russian equivalent of the NATO .50 BMG (12.7×99mm NATO) round. The differences between the two are the bullet shape, the types of powder used, and that the case of the 12.7×108mm is 9 mm longer and marginally more powerful.

12.7×108mm

: The 14.5×114 mm is a heavy machine gun and anti-materiel rifle round used by the Soviet Union, the former Warsaw Pact, modern Russia, and other countries. Its most common use is in the KPV heavy machine gun found on several Russian Military vehicles.