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Bullet

For other uses, see Bullet (disambiguation).
Bullet:.357 Magnum cartridges, containing bullets
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.357 Magnum cartridges, containing bullets

A bullet is a solid projectile propelled by a firearm and is normally made from metal (usually lead). A bullet (in contrast to a shell) does not contain explosives, and damages its target by imparting its kinetic energy upon impact.

The word "bullet" is often used loosely to refer to the combination of bullet, case, gunpowder and primer; such an item is properly called a cartridge, or round.


Contents

History

The first bullets

The history of bullets parallels the history of firearms. Advances in one either resulted from or precipitated advances in the other. Originally, bullets were round metallic or stone balls placed in front of an explosive charge of gun powder at the end of a closed tube. As firearms became more technologically advanced, from 1500 to 1800, the bullets changed little. They remained simple round lead balls, differing only in their size.

Bullet:Four 30-06 cartridges dated from the World War II era
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Four 30-06 cartridges dated from the World War II era

The development of the hand culverin and matchlock arquebus brought about the use of cast lead balls as projectiles. "Bullet" is derived from the French word "boulette" which roughly means "little ball". The original musket bullet was a spherical lead ball two sizes smaller than the bore, wrapped in a loosely fitting paper patch which formed a tight seal so the full pressure of the expanding gas would propel the bullet. The loading was, therefore, easy with the old smooth-bore Brown Bess and similar military muskets. The original muzzle-loading rifle, on the other hand, with a closely fitting ball to take the rifling grooves, was loaded with difficulty, particularly when foul, and for this reason was not generally used for military purposes. Even with the advent of rifling the bullet itself didn't change, but was wrapped in a cloth patch to grip the rifling grooves.

The first half of the nineteenth century saw a distinct change in the shape and function of the bullet. In 1826 Delirque, a French infantry officer, invented a breech with abrupt shoulders on which a spherical bullet was rammed down until it caught the rifling grooves. Delirque's method, however, deformed the bullet and was inaccurate.

Shaped bullets

Among the first "bullet-shaped" bullets was designed by Captain John Norton of the British Army in 1823. Norton's bullet had a hollow base which expanded under pressure to catch the rifling grooves once fired but the British Board of Ordnance rejected it because spherical bullets had been in use for the last 300 years.

Renowned English gunsmith William Greener invented the Greener bullet in 1836. It was very similar to Norton's bullet except that the hollow base of the bullet was fitted with a wooden plug which more reliably forced the base of the bullet to expand and catch the rifling. Tests proved that Greener's bullet was extremely effective but it was rejected because, being two parts, it was judged too complicated to produce.

The soft lead bullet that came to be known as the Minié ball, (or minnie ball) was first introduced in 1847 by Claude Étienne Minié (1814? - 1879), a captain in the French Army. It was nearly identical to the Greener bullet: as designed by Minié the bullet was conical in shape with a hollow cavity in the rear end, which was fitted with a little iron cap instead of a wooden plug. When fired, the cap would force itself into the hollow cavity, forcing the sides of the bullet to expand and engage the rifling. In 1855 the British adopted the Minié ball for their Enfield rifles.

It was in the American Civil War, however, that the Minié ball saw the most use. Roughly 90% of the battlefield casualties in the war were caused by Minié balls fired from rifles.

Bullet:.303 inch centrefire, rimmed ammunition
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.303 inch centrefire, rimmed ammunition

Between 1854 and 1857 Sir Joseph Whitworth conducted a long series of rifle experiments, and proved, among other points, the advantages of a smaller bore and, in particular, of an elongated bullet. The Whitworth bullet was made to fit the grooves of the rifle mechanically. The Whitworth rifle was never adopted by the government, although it was used extensively for match purposes and target practice between 1857 and 1866, when it was gradually superseded by Metford's.

About 1862 and later, W. E. Metford had carried out an exhaustive series of experiments on bullets and rifling, and had invented the important system of light rifling with increasing spiral, and a hardened bullet. The combined result of the above inventions was that in December 1888 the Lee Metford small-bore (0.303") rifle, Mark I, (photo of cartridge on right) was finally adopted for the British army. The Lee-Metford was the predecessor of the Lee-Enfield.

The modern bullet

The next important change in the history of the rifle bullet occurred in 1883, when Major Rubin, director of the Swiss Laboratory at Thun, invented the small-calibre rifle, one of whose essential features was the employment of an elongated compound bullet, with a lead core in a copper envelope called a jacket.

The copper jacketed bullet allows much higher muzzle velocities than lead alone, as copper has a much higher melting point, greater specific heat capacity, and is harder. Lead bullets fired at high velocity may suffer surface melting due to hot gases behind and friction with the bore.

European advances in aerodynamics led to the pointed ‘spitzer’ bullet. By the beginning of the twentieth century, most world armies had begun to transition to spitzer bullets. These bullets flew for greater distances more accurately and carried more energy with them. Spitzer bullets combined with machine guns increased the lethality of the battlefield exponentially.

The final advancement in bullet shape occurred with the development of the ‘boat tail’ which is a streamlined base for spitzer bullets. A vacuum is created when air strata moving at high speed passes over the end of a bullet. The streamlined boat tail design aims to eliminate this drag-inducing vacuum by allowing the air to flow alongside the surface of the tapering end, thus eliminating the need for air to turn around the 90-degree angle normally formed by the end of shaped bullets. The resulting aerodynamic advantage is currently seen as the optimum shape for rifle technology.

Design

Bullet:A modern cartridge is made up of five components:1. the bullet itself, which serves as the projectile; 2. the casing, which holds all parts together; 3. the propellant, for example gunpowder or cordite; 4. the rim, at the base of the cartridge; 5. the primer, which ignites the propellant.
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A modern cartridge is made up of five components:
1. the bullet itself, which serves as the projectile;
2. the casing, which holds all parts together;
3. the propellant, for example gunpowder or cordite;
4. the rim, at the base of the cartridge;
5. the primer, which ignites the propellant.

Bullet designs have to solve two primary problems. They must first form a seal with the gun's bore. The worse the seal, the more gas generated by the rapid combustion of the propellant charge leaks past the bullet reducing the efficiency. The bullet must also engage the rifling without damaging the gun's bore. Bullets must have a surface which will form this seal without causing excessive friction. What happens to a bullet inside the bore is termed internal ballistics. A bullet must also be consistent with the next bullet so that shots may be fired accurately.

Once it leaves the barrel, it is governed by external ballistics. Here, the bullet's shape is important for aerodynamics, as is the rotation imparted by the rifling. Rotational forces stabilize the bullet gyroscopically as well as aerodynamically. Any asymmetry in the bullet is largely cancelled as it spins. With smooth-bore firearms, a spherical shape was optimum because no matter how it was oriented, it presented a uniform front. These unstable bullets tumbled erratically, but the aerodynamic shape changed little giving moderate accuracy. Generally, bullet shapes are a compromise between aerodynamics, interior ballistics necessities, and terminal ballistics requirements. Another method of stabilization is for the center of mass of the bullet to be as far forward as practical as in the minnie ball or the shuttlecock. This allows the bullet to fly front-forward by means of aerodynamics.

See Terminal ballistics and/or Stopping power for an overview of how bullet design effects what happens when a bullet hits something, and how this is impacted by its design. What happens to the bullet is dictated as much by what it hits and how it hits, as by the bullet itself (just like how its interaction with air was critical in external ballistics). Bullets are generally designed to penetrate, deform, and/or break apart. For a given material and bullet, which of these happens is determined especially by the strike velocity.

Actual bullet shapes are many and varied, and an array of them can be found in any reloading manual that sells bullet moulds. RCBS are one of many makers, and the link will let you see many different designs, starting with the basic round ball. With a mould, bullets can be made at home for reloading your own ammunition, where local laws allow. Cast and jacketed bullets are also commercially available from numerous manufacturers for hand loading and are much more convenient than casting bullets from bulk lead.

Material

Bullets are classically moulded from an alloy of lead and tin. Typesetter's lead (used to mould Linotype), works very well. Lead is common because it is highly dense (providing a high amount of mass — and thus, kinetic energy — for a given volume) and is cheap to obtain and fabricate.

Treaties

The Geneva Accords on Humane Weaponry and the Hague Convention prohibit certain kinds of ammunition for use by uniformed military personnel against those uniformed military personnel of opposing forces. These include exploding, poisoned and expanding bullets. Nothing in these treaties prohibits incendiary bullets (tracers) or the use of prohibited bullets on military equipment.

Bullet acronyms

Figurative uses

The word for the bullet, usually because of its speed, is sometimes used figuratively, e.g.:-

References

  1. ^ : Hughes, David R. (1990). The History and Development of the M16 Rifle and its Cartridge, Oceanside, CA: Armory Publications.

This article incorporates text from the Encyclopædia Britannica Eleventh Edition, a publication now in the public domain.

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Wikipedia articles incorporating text from the 1911 Encyclopædia Britannica | Ammunition

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