Cartridge (weaponry)
A cartridge or round packages the bullet, gunpowder and primer of firearms in a single case made to a precise shape to fit the firing chamber of the firearm. The primer is a small charge of impact-sensitive chemical that may be located in the center of the case head in centerfire ammunition, or in its rim (also known as rimfire ammunition). (Electrically-fired cartridges have also been made; see below.) A cartridge without a bullet is called a blank.
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2 Cartridges in use 3 History 4 Problems 5 Reloading 6 Caseless ammunition 7 External link |
The cartridge 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 and the cartridge case is pulled out of the chamber.
Critical specifications include its calibre, bullet weight, expected velocity, maximum pressure, headspace, overall length and primer type. Diameter of a bullet is measured either as a decimal fraction of an inch, or in millimetres. The length of a cartridge case may also be designated in millimetres. Where two numbers are together, the first is the diameter, and the second is the cartridge length, e.g. 7.62x51mm.
Most high-powered guns have relatively small bullets moving at high speeds. This is because bullet energy increases proportionately to bullet weight, but as the square of velocity. Therefore, a bullet going twice as fast has four times the energy. 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.
The lethality of pistol ammunition is not limited by the ammunition, but by the accuracy and doctrine of the shooter. Rounds with these energies have insufficient momentum to knock people down (the recoil would break wrists), and move too slowly to cause significant hydrostatic shock.
There is great variety in the length and diameter of cartridges for the different kinds and calibres of rifles and pistols. The best cartridge for different purposes is subject to much discussion. However there are standard uses for certain calibres, 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. For example, a .22 pistol round is almost exactly the same caliber as a .223 NATO rifle round, but the .223 is vastly more powerful.
The following list samples only a few very well-known cartridges, for a complete list, see List of cartridges (weaponry), pistol and rifle. The list is roughly ordered by cartridge power.
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 flint-lock, about 1635, the priming was originally put into the pan of the wheel-lock and snaphance muskets from a flask containing a fine-grained powder called serpentine powder. Later the pan was filled from the cartridge above described before loading. The mechanism of the flint-lock musket, in which the pan was covered by the furrowed steel struck by the flint, 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 chlorate of potash, 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 chlorate of potash, 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, shot guns and pistols. 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 prevention of all escape of gas at the breech when the weapon is fired, by means of an expansive cartridge case containing its own means of ignition. Previous to this invention shot guns and sporting rifles were loaded by means of powder flasks and shot flasks, bullets, wads and copper caps, all carried separately. The earliest efficient modern cartridge case was the pin-fire, patented, according to some authorities, by Houiller, a Paris gunsmith, in 1847; and, according to others, by Lefaucheux, also a Paris gunsmith, in or about 1850. It consisted of 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.
The central-fire cartridge was introduced into England in 1861 by Daw. It is said to have been the invention of Pottet of Paris, improved upon by Schneider, and gave rise to much litigation in respect of its patent rights. Daw was subsequently defeated in his control of the patents by Eley Bros. In this cartridge the cap in the centre of the cartridge base is detonated by a striker passing through the standing breech to the inner face, the cartridge case being withdrawn, or, in the most modern weapons, ejected by a sliding extractor fitted to the breech end of the barrel, which catches the rim of the base of the cartridge.
This is practically the modern cartridge case now in universal use. In the case of shot guns it has been gradually improved in small details. The cases are made either of paper of various qualities with brass bases, or entirely of thin brass. The wadding between powder and shot has been thickened and improved in quality; and the end of the cartridge case is now made to fit more perfectly into the breech chamber. These cartridges vary in size from 32 bore up to 4 bore for shoulder guns. They are also made as small as .410 and .360 gauge: their length varies from 1¾ inches to 4 inches Cartridges for punt guns are usually 1½ inches in diameter and 9¾ inches in length.
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 1867 the British war office adopted the Eley-Boxer metallic central-fire cartridge case in the Enfield rifles, which were converted to 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. Later the solid-drawn, central-fire cartridge case, made of one entire solid piece of tough hard metal, an alloy of copper, &c., with a solid head of thicker metal, has been generally substituted.
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.
The conventional cartridge also adds certain problems to the gun.
Also, it had become well-known that the cartridge is both expensive and heavy, and the single most difficult part to manufacture. Generally, they were manufactured by deforming a disk of brass with a series of progressive dies. Cases are generally round, and this decreases the volumetric efficiency of the gun's magazine. A caseless cartridge can have the propellant molded in a square shape.
The gun has to have an ejection port to eliminate the spent cartridge-case. This means that dirt and fluid can enter the gun through the ejection port.
The primer, and associated firing pin add a delay between the time the trigger is pressed and the time the bullet leaves the barrel. Experiments had decisively demonstrated that this delay reduced accuracy for most shooters. A popular accessory, available for many guns, were "low mass" firing pins and hammers, often made of titanium, that would reduce the time to fire the percussion cap.
On the flip side, the case helps carry heat away from the firing chamber.
Some shooting enthusiasts reload their spent brass cartridges. By using a press and a set of dies, one can reshape, deprime, reprime, charge the case with fresh powder, and seat and crimp a new bullet. One can do this at about half the cost of purchasing factory ammo. It also allows one to use differnt weights and styles of bullets, as well as varying the powder charge which affects accuracy and power.
Around 1989, Heckler und Koch, a prominent German firearms manufacturer, began making press releases about the G11 assault rifle, which shot a 4.75x33 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 volts. +/- 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, making any shooter more accurate.
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.
Design
Rimmed, centrefire .303in cartridge from WWII
Cartridges in use
See also: List of cartridges (weaponry), pistol and rifleHistory
Problems
Reloading
Caseless ammunition
External link