Bullet

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A bullet is a solid projectile propelled by a firearm and is normally made from metal (usually lead).

Explanation

A bullet (in contrast to a shell) does not contain explosives . The term 'bullet' refers specifically to the metal slug that is propelled from a firearm.

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

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.

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 leather 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 minie ball for their Enfield rifles.

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

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 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 explosion 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 asymetry 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 a popular choice 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.

Lead: Simple cast, extruded, swaged, or otherwise fabricated lead slugs are the simplest form of bullets. At speeds of greater than 300 m/s (1000 ft/s) (common in most handguns), lead is deposited in rifled bores at an ever increasing rate. Alloying the lead with a small percentage of tin and/or antimony helps this situation somewhat, but is not completely effective as velocities are increased. A gas check may be used for some lead bullets, but are only useful up to a certain muzzle velocity, as they only protect the base of the bullet from melting, not the sides. It normally takes the form of a very thin copper disc attached to the rear of the bullet.

Jacketed Lead: Bullets intended for high-velocity applications generally have a lead core jacketed or plated with copper or steel; the thin layer of copper protects the lead core during flight, delivering it intact to the target. There, the heavy lead core delivers its kinetic energy to the target. FMJ bullets have the front and sides of the bullet completely encased in the jacket. Some bullet jackets do not extend to the front of the bullet to aid in expansion. These are called soft points or hollow points. Steel bullets are often plated with copper or other metals for corrosion resistance.

Armor Piercing: Jacketed designs where the core material is a very hard and high-density metal such as tungsten, tungsten carbide, depleted uranium, or steel. A pointed tip is often used, but a flat tip on the penetrator portion is actually more effective.

Tracer: These have a hollow back, filled with a flare material. Usually this is a mixture of magnesium, perchlorate, and chromium, to yield a bright red color. Tracer material burns out after a certain amount of time.

Incendiary: These bullets are made with an explosive or flammable mixture in the tip which is designed to ignite on contact with a target. The intent is to ignite fuel in the target area and add to the destructive power of the bullet itself.

Frangible: Designed to disintegrate into tiny particles upon impact to minimize their penetration for reasons of range safety, to limit environmental impact, or to limit the danger behind the intended target. An example is the Glaser Safety Slug.

Non Toxic: Bismuth, tungsten, steel, and other exotic bullet alloys prevent release of toxic lead into the environment. Regulations in several countries around the world mandate the use of non-toxic projectiles especially when used against waterfowl. It has been found that birds swallow shot for their gizzards and the effects of lead poisoning are magnified.

Practice: Made from lightweight materials like rubber, Wax, wood, plastic, or lightweight metal bullets are intended for short-range target work. Because of their weight and low velocity, they have limited range.

Less Lethal: Rubber bullets, plastic bullets, and beanbags are designed to be non-lethal, for example for use in riot control. They are generally low velocity fired from shotguns, grenade launchers, paintball guns, or specially designed devices.

Blanks: Wax, paper, plastic, and other materials are used to simulate live gunfire and are intended only to hold back the powder in a blank cartridge and produce noise. The 'bullet' may be captured in a purpose-designed device or it may be allowed to expend what little energy it has in the air. Some blank cartridges are crimped or closed at the end and do not have any plug material.

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 or the use of prohibited bullets on military equipment.

Bullet acronyms

ACC — Accelerator
BBWC — Bevel Base Wadcutter
BEB — Brass Enclosed Base
BT — Boat-Tail
BTHP — Boat Tail Hollow Point
CB — Cast Bullet
CL — Core-Lokt
DEWC — Double Ended Wadcutter
FMJ — Full Metal Jacket
FN — Flat Nose
FP — Flat Point
FST — Fail Safe Talon
GD — Gold Dot
GDHP — Gold Dot Hollow Point
GS — Golden Saber
HBWC — Hollow Base Wadcutter
HC — Hard Cast
HP — Hollow Point
HPJ — High Performance Jacketed
HS — Hydra Shok
J — Jacketed
JFP — Jacketed Flat Point
JHC — Jacketed Hollow Cavity
JHP — Jacketed Hollow Point
JSP — Jacketed Soft Point
L — Lead
L-T — Lead Combat
L-T — Lead Target
LFN — Long Flat Nose
LFP — Lead Flat Point
LHP — Lead Hollow Point
LRN — Lead Round Nose
LSWC — Lead Semi-Wadcutter
LSWC-GC — Lead Semi-Wadcutter Gas Checked
LWC — Lead WadCutter
LTC — Lead Truncated Cone
MC — Metal Cased
MRWC — Mid-Range Wadcutter
PB — Lead Bullet
PB — Parabellum
PL — Power-Lokt
PSP — Plated Soft Point
PSP — Pointed Soft Point
RN — Round Nose
RNFP — Round Nose Flat Point
RNL — Round Nosed Lead
SJ — Semi Jacketed
SJHP — Semi Jacketed Hollow Point
SJSP — Semi-Jacketed Soft Point
SP — Soft Point
SP — Spire Point
SPTZ — Spitzer
ST — Silver Tip
STHP — Silver Tip Hollow Point
SWC — Semi Wadcutter
SX — Super Explosive
SXT — Supreme Expansion Talon
TC — Truncated Cone
TMJ — Total Metal Jacket
VLD — Very Low Drag
WC — Wadcutter
WLN — Wide Long Nose
XTP — Extreme Terminal Performance

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