Cartridge (firearms)

From left: .50 BMG, .300 Win Mag, .308 Winchester, 7.62x39mm, 5.56x45mm NATO, .22LR.

A cartridge, also called a round, packages the bullet, gunpowder and primer into a single metallic case precisely made to fit the firing chamber of a firearm. The primer is a small charge of impact-sensitive chemical that may be located at the center of the case head (centerfire ammunition) or at its rim (rimfire ammunition). Electrically-fired cartridges have also been made. A cartridge without a bullet is called a blank; one that is completely inert is called a dummy.

Contents

Design

.30-06 Springfield cartridge specifications. This is a rimless cartridge case. Measurements are in inches.

The cartridge case seals a firing chamber in all directions except down the bore. A firing pin strikes the primer, igniting it. The spark from the primer ignites the powder. Burning gases from the powder expand the case to seal against the chamber wall. The projectile is then pushed in the direction that releases this pressure, down the barrel. After the projectile leaves the barrel the pressure is released, allowing the cartridge case to be removed from the chamber.

An M4 Carbine, with an ejected case visible in mid-air.
Various cases of assorted common calibers.
Aluminum .44 caliber cases.

Automatic and semiautomatic firearms, which extract and eject the case automatically as a part of their operation, sometimes damage the case in the process of ejection. Brass is a commonly used material, as it is ductile enough to be reformed and reloaded several times. However, some low-quality "plinking" ammunition, as well as some military ammunition (mainly from the former Soviet Union and Communist China) is made with steel cases because steel is less expensive than brass. As militaries typically consider small arms cartridge cases to be a disposable, one-time-use affair, the lack of ductility is inconsequential for this application. Some ammunition is also made with aluminum cases (see picture).

Critical specifications include caliber, bullet weight, expected velocity, maximum pressure, headspace, overall length and primer type. A minor deviation in many of these specifications could result in damage to the firearm, and in extreme cases injury or death of the user. The diameter of a bullet is measured either as a decimal fraction of an inch, or in millimeters. The length of a cartridge case may also be designated in millimeters.

Where two numbers are together, the second number can contain a variety of meanings. Frequently the first is the diameter (caliber) of the cartridge, and the second is the length of the cartridge case. For example, the 7.62 x 51 mm uses a bore diameter of 7.62 mm and has an overall case length of 51 mm. In the case of old black powder cartridges, the second number typically refers to the powder charge. For example, the .50-90 Sharps is a .50 caliber bullet (.512) with a nominal charge of 90 grains (5.8 g) of black powder with a case length of 2.50 inches (64 mm).

One should be aware that cartridge nomenclature is inconsistent and unhelpful when trying to determine dimensions, tolerances or indeed almost any other characteristic of a given round. The .38 Special actually has a bullet diameter of 0.357 inches (9.1 mm) (jacketed) or 0.358 inches (9.1 mm) (lead) while the case has a diameter of 0.380 inches (9.7 mm). The .357 Magnum is a direct evolution of the .38 special, but differently named, and no reference is made to the longer case. The .30-06 rifle round is a (nominally) .30 inches (7.6 mm) caliber round designed in 1906; and the .303 British round may vary wildly in actual dimensions (as do the surviving rifle chambers of its era).

Most high-powered guns have relatively small bullets moving at high speeds. This is because while bullet energy increases in direct proportion to bullet weight, it increases in proportion to the square of bullet velocity. Therefore, a bullet going twice as fast has four times the energy (see physics of firearms). Bullet speeds are now limited by starting bore pressures, which in turn are limited by the strength of materials and the weight of gun people are willing to carry. Larger cartridges have more powder, and usually higher velocities.

Of the hundreds of different designs and developments that have occurred, essentially only two basic cartridge designs remain. All current firearms are either rimfire or centerfire. US military small arms suppliers are still trying to perfect electronic firing, which replaces the conventional firing pin and primer with an electrical ignition system wherein an electrical charge ignites the primer.

Centerfire

Rimmed, centerfire .303 cartridge from WWII. Manufactured by Colonial Ammunition Company, New Zealand.
Main article: Centerfire ammunition

A centerfire cartridge has a centrally located primer, which in most US made ammunition, and in some (chiefly premium hunting and match ammunition) manufactured in other countries, can be replaced, so that the expensive brass cartridge case can be reused. Such a cartridge is said to be Boxer primed. Most European and Asian military ammunition uses a non-replaceable Berdan primer, which prevents the easy reuse of the case, because the anvil of the primer is an integral part of the case and can be deformed by firing. With care, it can be reloaded. An irregular fighter might more simply reload a Berdan-primed cartridge, since the new "primer" can be as simple as a bit of tin can and a match head, without the multi-stage process required for making a Boxer primer. US military ammunition is Boxer primed.

Rimfire

Main article: Rimfire ammunition

Rimfire cartridges, of which only the popular .22 LR remains in common use, were a popular solution before the centerfire design was fully perfected. They can only be used for fairly low powered cartridges, as the case has to be soft enough to be deformed by the firing pin, which detonates the priming compound in the rim. In the past, 9 mm cartridges were available, as well as .177, .25, etc. cartridges. BB and CB caps were common, as well as .22 Short and .22 Long.

Today, .22 LR (Long Rifle)accounts for much of rimfire ammunition shot. Recently, a .17 HMR (nominally .172 caliber) rimfire cartridge was released, and has become extremely popular among target shooters as well as small game hunters, due to its high velocity and flat shooting characteristics. .22 LR rounds normally use a soft lead bullet, and can be supersonic or subsonic. They are often copper-washed both for toxicity reasons and to prevent barrel fouling. .22 Magnum cartridges typically contain copper jacketed lead projectiles. The newer .17 rounds all feature bullets similar in construction to those found in centerfire cartridges, such as copper jacketed lead..

Semi-automatic vs. Revolver Cartridges

Nearly every semi-automatic pistol cartridge is "rimless", or more explicitly has an inset rim that the extractor engages. Revolver cartridges, on the other hand, have a rim at the base of the case which seats into the cylinder block to keep the cartridge from moving too forward in the cylinder. For a visual comparison of similar-sized cartridges with different rims, see .380 ACP (semi-automatic) vs. .38 Special (revolver.)

Cartridges in use

See also table of pistol and rifle cartridges by year

There is great variety in the length and diameter of cartridges for the different kinds and calibers of rifles and pistols. The best cartridge for different purposes is subject to much discussion. However, there are standard uses for certain calibers, and these are a reliable guide to recommended uses.

It is important to note that equivalent caliber is by no means equivalent power. Generally speaking, "stopping power" is determined by the weight of the bullet, the terminal ballistics of the bullet – does it stay straight and in one piece, tumble, or "mushroom" on impact – and the charge of gunpowder accelerating it.

The following list samples only a few very well-known cartridges; for a complete list, see table of pistol and rifle cartridges by year. The list is roughly ordered by cartridge length.

Jacketing Of Cartridges' Bullets

A cutaway showing a Japanese Navy 7.7 mm rimed rounds as fired by the Type 92 and Type 97 machine guns - copies of Vickers and Lewis designs. The round is effectively interchangeable with .303 British
000 Buck  - 8 lead pellets (0.36 in/9.1 mm)
00 Buck - 9 lead pellets (0.33 in/8.4 mm)
0 Buck - 12 lead pellets (0.32 in/8.1 mm)
1 Buck - 16 lead pellets (0.30 in/7.6 mm)
4 Buck - 27 lead pellets (0.24 in/6.1 mm)
QB 8 - 8 pellets (Armor Piercing) - Quadrangle Buck is made from a steel cylinder cut into two layers of four pie-shaped pieces per layer. The numerous sharp edges gives excellent penetration; however, the light weight and poor ballistic shape limits its effective range.

Flechettes - 32 flechettes (Armor Piercing) - Flechettes are essentially small steel nails with tiny fins swaged into the rear.

Slug - Slugs will pretty well flatten any target, armored or not; however, the issue of over penetration will determine whether you want to take the solid or the hollow-point slug.

Slug HP - Hollow-point slugs. Less penetration than regular slugs.

Baton - Rubber batons. Used for training.

Calibers

Ammunition types are listed numerically.

History

The original cartridge for military small arms dates from 1586. It 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.

This cartridge was used with the muzzle-loading military firearm, the base of the cartridge being ripped or bitten off by the soldier, the powder poured into the barrel, and the bullet then rammed home. Before the invention of the firelock or flintlock, about 1635, the priming was originally put into the pan of the wheellock and snaphance muskets from a flask containing a fine-grained powder called serpentine powder.

The evolving nature of warfare required a firearm which could be fired 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 weapon. 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 which 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, sulphur and charcoal, which exploded 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 by a perforated nipple, and by replacing the cock or hammer which held the flint by a smaller hammer with a hollow to fit on the nipple when released by the trigger. On the nipple was placed the copper cap containing the detonating composition, now made of three parts of potassium chlorate, two of fulminate of mercury and one of powdered glass. 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.

Integrated paper cartridges

Chassepot paper cartridge (1866).

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:[2] the cartridges incorporated a copper base with integrated mercury fulminate primer powder (the major innovation of Pauly), a paper casing and a round bullet.[3] The cartridge was loaded through the breech and fired with a needle. The needle-activated central-fire breech-loading gun would become a major feature of firearms thereafter.[4] Pauly made an improved version which was protected by a patent on 29 September 1812.[2]

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 gunmaking, 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 the preventing gas escaping the breech when the weapon 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 flasks, bullets, wads and copper caps, all carried separately. One of the earliest efficient modern cartridge case was the pin-fire cartridge, developed by French gunsmith Casimir Lefaucheux in 1836.[5]. It consisted of a thin weak shell made of brass and paper which expanded by the force of the explosion, fitted perfectly into 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 exploded 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 1855. Later in 1846, M.Houiller, another Paris gunsmith, improved on the system by introducing a fully metallic cartridge in 1847.[6]

A diagram of a Dreyse needle gun cartridge, showing the paper cartridge case, the sabot, and acorn-shaped bullet.

As a result of the relatively low pressures involved, cartridges used in modern shotguns have changed very little since the invention of the center-fire primer. The only changes are that the cases may be made of paper, plastic, and/or metal; the wadding between powder and shot is now made of modern materials; and the end of the cartridge case is more precisely fitted to the breech chamber, which ranges in modern shotguns from .410-inch (10.4 mm) bore to various gauges, 10 gauge being the largest still used in modern shoulder-held shotguns (smaller gauges have industrial uses). Gauge is measured by the number of equal-sized balls that can be formed from a pound of pure lead; a 12-gauge shotgun has a bore of .729 inches (18.5 mm), which is the diameter of a 1⁄12-pound (38 g) ball of lead; a 10 gauge fits one of 10 balls produced from a pound (460 g) of lead (.775 inches/19.7 millimetres bore).

Rifle cartridges, on the other hand, have undergone significant changes as the pressures involved have increased. In the case of military rifles the breech-loading cartridge case was first adopted in principle by the Prussians about 1841 in the needle-gun breech-loader. In this a conical bullet rested on a thick wad, behind which was the powder, the whole being enclosed in strong lubricated paper. The detonator was in the hinder surface of the wad, and fired by a needle driven forward from the breech, through the base of the cartridge and through the powder, by the action of a spiral spring set free by the pulling of the trigger.

In the American Civil War (1861-65) a breechloading 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 and Wesson (amongst many others) of revolver handguns that used metal cartridges helped to establish cartridge firearms as the standard in the USA by the 1870's although many continued to use percussion revolvers well after that.

Full metal cartridges

(From Left to Right): A .577 Snider cartridge (1867), a .577/450 Martini-Henry cartridge (1871), a later drawn brass .577/450 Martini-Henry cartridge, and a .303 British Mk VII SAA Ball cartridge.
French Army Fusil Gras mle 1874 metallic cartridge.

In 1867 the British war office adopted the Eley-Boxer metallic central-fire cartridge case in the 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 detonating cap was in the base of the cartridge, and was exploded 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 casing upon firing. Later the solid-drawn, central-fire 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.

The 8 mm Lebel ammunition, developed in 1886, the first smokeless gunpowder cartridge to be made and adopted by any country.

Central-fire cartridges with solid-drawn metallic cases containing their own means of ignition are almost universally used in all modern varieties of military and sporting rifles and pistols.

Around 1970, 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.

Reloading

Some shooting enthusiasts reload their spent brass cartridges. By using a press and a set of dies, one can reshape, deprime, reprime, recharge the case with gunpowder, and seat and crimp a new bullet. One can do this at about half the cost of purchasing factory ammunition. It also allows one to use different weights and shapes of bullets, as well as varying the powder charge which affects accuracy and power. Enthusiasts usually only reload boxer primed cartridges as the process is more easily automated than berdan priming.

See also: Handloading

Caseless ammunition

Main article: Caseless ammunition

Around 1989, Heckler & Koch, a prominent German firearms manufacturer, began making press releases about the G11 assault rifle, which shot a 4.73x33 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 reaction time (lock time), and allowing for easier adjustment of the rifle trigger.

In both cases, 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.

Trounds

Main article: Dardick tround

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 shape, and were made of plastic or aluminium, 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.

Blank ammunition

Main article: Blank (cartridge)
Blank cartridges:

A blank is a charged cartridge that does not contain a projectile — the opening where the projectile would be held is crimped shut or sealed with some material that will disperse rapidly upon leaving the barrel, in order to contain the propellant. This sealing material can still potentially cause harm at extremely close range. Blanks are used in training, but do not always cause a weapon to behave in an identical way to when using live ammunition; recoil will almost always be far weaker, and some automatic weapons will only cycle correctly when the weapon is fitted with a blank-firing adaptor to confine gas pressure within the barrel in order to operate the gas system. Blanks may 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 explode instead of propelling it forward. Blanks may also be used in dedicated launchers for propelling a grapnel, rope line or flare, or for a training lure for training gun dogs. The propellant cartridges used in a heavier variety of nail gun are essentially rimfire blanks.

Drill rounds

Drill rounds are inert versions of cartridges used for education and practice during military training. Other than the lack of propellant, they are the same size as normal cartridges and will fit into the mechanism of a weapon in the same way as a live cartridge. To distinguish them from live rounds they are marked distinctively. Several forms of markings may be used; eg setting coloured flutes in the cartridge, drilling holes through the cartridge, colouring the bullet or cartridge, or a combination of these. In the case of centrefire drill rounds the primer will often be absent, its mounting hole in the base left open. Because they 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 need to be frequently inspected to ensure they are not so degraded as to become unusable - for example the casings can become torn or misshapen and snag on moving parts, or the bullet can become separated and stay in the breech when the cartridge is ejected.

See also

References

  1. ↑ The US didn't sign the complete Hague Accords in any case, but still follows its guidelines in military conflicts.
  2. ↑ 2.0 2.1 Chemical Analysis of Firearms, Ammunition, and Gunshot Residue by James Smyth Wallace Page 24 [1]
  3. ↑ Firearms by Roger Pauly p.94 [2]
  4. ↑ A History of Firearms By W. Y. Carman p.121 [3]
  5. ↑ Pistols by Jeff Kinard p.109 [4]
  6. ↑ Pistols by Jeff Kinard p.109 [5]

External links