A cast bullet is made by allowing molten metal to solidify in a mould

Molding (process)

Molding or moulding is the process of manufacturing by shaping pliable raw material using a rigid frame or model called a pattern....

. Most cast bullets are made of lead

Lead

Lead is a main-group element in the carbon group with the symbol Pb and atomic number 82. Lead is a soft, malleable poor metal. It is also counted as one of the heavy metals. Metallic lead has a bluish-white color after being freshly cut, but it soon tarnishes to a dull grayish color when exposed...

 alloyed with tin

Tin

Tin is a chemical element with the symbol Sn and atomic number 50. It is a main group metal in group 14 of the periodic table. Tin shows chemical similarity to both neighboring group 14 elements, germanium and lead and has two possible oxidation states, +2 and the slightly more stable +4...

 and antimony

Antimony

Antimony is a toxic chemical element with the symbol Sb and an atomic number of 51. A lustrous grey metalloid, it is found in nature mainly as the sulfide mineral stibnite...

; but zinc

Zinc

Zinc , or spelter , is a metallic chemical element; it has the symbol Zn and atomic number 30. It is the first element in group 12 of the periodic table. Zinc is, in some respects, chemically similar to magnesium, because its ion is of similar size and its only common oxidation state is +2...

 alloys have been used when lead is scarce, and may be used again in response to concerns about lead toxicity. Most commercial bullet manufacturers use swaging in preference to casting, but bullet casting remains popular with handloaders

Handloading

Handloading or reloading is the process of loading firearm cartridges or shotgun shells by assembling the individual components , rather than purchasing completely assembled, factory-loaded cartridges...

.

History

Firearms projectiles were being cast in the 14th century. Iron

Iron

Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

 was used for cannon

Cannon

A cannon is any piece of artillery that uses gunpowder or other usually explosive-based propellents to launch a projectile. Cannon vary in caliber, range, mobility, rate of fire, angle of fire, and firepower; different forms of cannon combine and balance these attributes in varying degrees,...

, while lead was the preferred material for small arms. Lead was more expensive than iron, but it was softer and less damaging to the relatively weak iron barrels of early musket

Musket

A musket is a muzzle-loaded, smooth bore long gun, fired from the shoulder. Muskets were designed for use by infantry. A soldier armed with a musket had the designation musketman or musketeer....

s. Lead could be cast in a ladle over a wood fire used for cooking or home heating, while casting iron required higher temperatures. Greater density of lead allowed lead bullets to retain velocity and energy better than iron bullets of the same weight and initial firing velocity.

Swaging, rather than casting, became a preferred manufacturing technique during the 19th century industrial revolution

Industrial Revolution

The Industrial Revolution was a period from the 18th to the 19th century where major changes in agriculture, manufacturing, mining, transportation, and technology had a profound effect on the social, economic and cultural conditions of the times...

; but lead bullets remained popular in early rimmed black powder cartridges like the .32-20 Winchester

.32-20 Winchester

The .32-20 Winchester, also known as the .32 WCF , was the first small-game lever-action cartridge thatWinchester produced. It was initially introduced as a blackpowder cartridge in 1882 for small-game, varmint hunting, and deer. Colt produced a single-action pistol chambered for this cartridge a...

, .32-40 Ballard

.32-40 Ballard

The .32-40 Ballard is an American rifle cartridge.Introduced in 1884, the .32-40 was developed as a black powder match-grade round for the Ballard single-shot Union Hill No. 8 and 9 target rifles...

, .38-40 Winchester

.38-40 Winchester

The .38-40 Winchester is actually a .40 caliber cartridge shooting .401 caliber bullets. The cartridge that was introduced by Winchester in 1874 and is derived from their .44-40 Winchester. This cartridge was introduced for rifles, but in its reintroduction for Cowboy Action Shooting it has seen...

, .38-55 Winchester

.38-55 Winchester

The .38-55 Winchester cartridge is named for its approximately .38 caliber bullet and was introduced in 1876 by Ballard which belonged to Marlin Firearms from 1875 on for various single-shot target rifles and in their 1893 lever action. It was later used by Winchester for its Model 1894...

, .44-40 Winchester

.44-40 Winchester

The .44-40 Winchester, also known as the .44 Winchester, the .44 WCF , and the .44 Largo was introduced in 1873 by the Winchester Repeating Arms Company. It was the first centerfire metallic cartridge offered by Winchester,and was brought out as the standard chambering for the new Winchester Model...

, .45 Colt

.45 Colt

The .45 Colt cartridge is a handgun cartridge dating to 1872. It began as a black powder revolver round developed for the Colt Single Action Army revolver, but is offered as a magnum level handgun hunting round in modern usage. This cartridge was adopted by the U.S. Army in 1873 and served as the...

, and .45-70

.45-70

The .45-70 rifle cartridge, also known as .45-70 Government, was developed at the U.S. Army's Springfield Armory for use in the Springfield Model 1873...

. Disadvantages became evident as loadings shifted to smokeless powder

Smokeless powder

Smokeless powder is the name given to a number of propellants used in firearms and artillery which produce negligible smoke when fired, unlike the older gunpowder which they replaced...

 in the late 19th century. Higher velocity smokeless powder loadings caused lead to melt and be torn from soft bullets to remain in the barrel after firing in small deposits called leading.. Manufacturers of high-velocity military ammunition modified their bullet swaging process to apply a thin sheet of stronger metal over the soft lead bullet. Although it took several decades to devise bullet jacket alloys and manufacturing procedures to duplicate the accuracy of cast bullets at lower velocities; jacketed bullets were more accurate at the velocity of 20th century military rifle cartridges. Jacketed bullets also functioned more reliably and are less likely to be deformed in the mechanical loading process of self-loading pistols and machine-guns.

Cast bullet advantages

Bullet casting remained popular for shooters accustomed to older weapons. Firearms were often sold with a mould designed for that particular weapon; so individuals living in remote areas would be able to manufacture their own ammunition rather than relying upon undependable supplies from local merchants. The uniform fit of bullets from an individual mould offered superior accuracy when early manufacturing tolerances were comparatively large.

These basic advantages remain true today. Moulds can be obtained to uniformly cast bullets of a diameter producing optimum accuracy in a specific firearm, and a firearm owner possessing such a mould can obtain a supply of those bullets independent of unreliable manufacturers and distributors. Bullets cast over a fireplace or stove from readily obtainable scrap materials still offer excellent performance in subsonic revolver cartridges, and more sophisticated casting techniques can produce bullets suitable for loading at velocities up to about 600 metres (2000 feet) per second.

Safety

Although some bullet casting procedures can be accomplished with heating elements used for cooking; care must be taken to avoid contaminating food preparation areas and/or utensils with lead alloys. Most bullet casters prefer to use portable electric melting pots in areas with good ventilation. Molten metal can cause serious burns; and molten metal can be sprayed around the working area by violently expanding steam if it comes in contact with water from spilled drinks or other sources. Bullet casters should wear protective clothing including eye protection, and should carefully wash hands prior to eating, drinking, or smoking. Young children are especially vulnerable to lead poisoning and are unlikely to appreciate the danger of shiny molten metal and newly cast bullets. Bullet casting must be limited to times and locations when children are absent.
Particular risk comes from the oxides of lead and other metals present in lead alloys, as oxides are often more easily absorbed than the metallic forms. This means that the dross that is skimmed from the lead pot may pose a larger hazard than the metallic alloys.

Bullet shapes

Cast bullets require a longer bearing surface than jacketed bullets to maintain an equivalent alignment with the bore of the firearm; because the softer cast bullet can be more readily deformed. The most successful cast bullet designs have a round or flatened nose rather than a long, unsupported ogive. Bullet designs with a forward diameter designed to be supported on the rifling lands work best in barrels rifled with wide lands and narrow grooves like the 2-groove M1903-A3 rifles. Forward bearing surfaces of full groove diameter provide more effective alignment in barrels with wide grooves and narrow lands, provided the chamber throat is long enough to accept such bullets.

Gas checks

One of the earlier efforts to obtain better high-velocity performance involves placing a very shallow cup of copper alloy over the base of the bullet. This cup resembles a very short jacket, and is called a gas check. Cast bullets require a smaller diameter at the base to accept the gas check. Some gas checks are designed to crimp onto the base of the bullet, while others have a looser fit.

Bullet alloys

Pure lead was used to cast hollow base bullets for Civil War era muskets. These bullets were designed to load easily and then expand into the grooves of the rifling when fired. Pure lead is undesirably soft for casting bullets not requiring such expansion. Tin is a common alloying element. Lead alloyed with a small amount of tin fills out moulds more uniformly than pure lead. Tin also increases the hardness of cast bullets up to a maximum at about eight to ten percent tin. Tin is relatively expensive, so many modern alloys rely upon antimony to increase hardness while retaining the casting advantages of a minimal addition of tin. Linotype

Linotype (alloy)

Linotype or eutectic alloy is a broad name applied to five categories of lead alloys used in manufacture of type, each with three to five sub-classifications....

 metal is a eutectic alloy of 3% tin, 12% antimony, and 85% lead. It is a very satisfactory alloy for casting most bullets. However, bullets from Linotype alloy tend to be brittle, and not suitable for some game hunting.

Heat Treating

Heat treating can increase the hardness of commonly used lead alloys. The basic procedure is to rapidly cool, or quench

Quench

In materials science, quenching is the rapid cooling of a workpiece to obtain certain material properties. It prevents low-temperature processes, such as phase transformations, from occurring by only providing a narrow window of time in which the reaction is both thermodynamically favorable and...

, hot bullets. Some suggest this can be done by dropping hot bullets from the mold into a tub of water; but this procedure carries the risk of splashing water onto the mold or into the molten casting metal and causing a steam explosion. An alternative procedure is to re-heat cast bullets (usually in a wire mesh basket) in a temperature-controlled oven and then remove and quench. The oven temperature should be less than the melting temperature of the bullet alloy. This temperature will vary with the concentrations of alloying elements; but is often in the range of 450 to 500 degrees Fahrenheit (230 to 260 degrees Celsius).

Bullet lubrication

Tallow

Tallow

Tallow is a rendered form of beef or mutton fat, processed from suet. It is solid at room temperature. Unlike suet, tallow can be stored for extended periods without the need for refrigeration to prevent decomposition, provided it is kept in an airtight container to prevent oxidation.In industry,...

 or lard

Lard

Lard is pig fat in both its rendered and unrendered forms. Lard was commonly used in many cuisines as a cooking fat or shortening, or as a spread similar to butter. Its use in contemporary cuisine has diminished because of health concerns posed by its saturated-fat content and its often negative...

 was used as a lubricant to ease the insertion of muzzle loaded bullets. Elongated rifle bullets were designed to be cast with grooves encircling the bullet to provide a reservoir for lubricant. These lubricants softened the black powder fouling for easier removal and reduced the tendency of bullets to leave deposits of lead in the barrel as they were fired. The latter advantage continued to be significant with smokeless powder. Attempts to obtain satisfactory high-velocity performance with cast bullets have included experimentation with a variety of lubricant mixtures including such things as beeswax

Beeswax

Beeswax is a natural wax produced in the bee hive of honey bees of the genus Apis. It is mainly esters of fatty acids and various long chain alcohols...

, carnuba wax, Japan wax

Japan wax

Japan wax is a pale-yellow, waxy, water-insoluble solid with a gummy feel, obtained from the berries of certain sumacs native to Japan and China, such as Rhus verniciflua and R. succedanea ....

, bayberry wax, paraffin

Paraffin

In chemistry, paraffin is a term that can be used synonymously with "alkane", indicating hydrocarbons with the general formula CnH2n+2. Paraffin wax refers to a mixture of alkanes that falls within the 20 ≤ n ≤ 40 range; they are found in the solid state at room temperature and begin to enter the...

, petroleum jelly

Petroleum jelly

Petroleum jelly, petrolatum, white petrolatum or soft paraffin, CAS number 8009-03-8, is a semi-solid mixture of hydrocarbons , originally promoted as a topical ointment for its healing properties...

, sperm oil, castor oil

Castor oil

Castor oil is a vegetable oil obtained from the castor bean . Castor oil is a colorless to very pale yellow liquid with mild or no odor or taste. Its boiling point is and its density is 961 kg/m3...

, stearyl alcohol, lauryl alcohol, graphite

Graphite

The mineral graphite is one of the allotropes of carbon. It was named by Abraham Gottlob Werner in 1789 from the Ancient Greek γράφω , "to draw/write", for its use in pencils, where it is commonly called lead . Unlike diamond , graphite is an electrical conductor, a semimetal...

, molybdenum disulphide, mica

Mica

The mica group of sheet silicate minerals includes several closely related materials having highly perfect basal cleavage. All are monoclinic, with a tendency towards pseudohexagonal crystals, and are similar in chemical composition...

, zinc oxide

Zinc oxide

Zinc oxide is an inorganic compound with the formula ZnO. It is a white powder that is insoluble in water. The powder is widely used as an additive into numerous materials and products including plastics, ceramics, glass, cement, rubber , lubricants, paints, ointments, adhesives, sealants,...

, Teflon, cup grease, lithium soap, water pump grease, and a variety of more modern lubricating materials.

Paper-patched bullets

One of the earlier attempts to obtain better high-velocity performance with cast bullets involved applying paper jackets. Swaging was not a successful means of applying paper jackets; since paper has lower tensile strength than metal. Patching is the term used to describe the hand process of applying paper jackets. The bullet must be cast of a smaller diameter than the bore to be brought up to bore diameter by a uniform number of paper wrappings. A relatively strong paper, such as that used for paper money, is precisely cut to wrap almost twice around the bullet. The width of the piece of paper is slightly greater than the bearing surface of the bullet; so some paper extends past the base of the bullet. This paper patch is moistened with a lubricant to make it more pliable and slightly sticky. The patch is carefully wrapped around the bearing surface of the bullet. The lip of paper extending past the base of the bullet is then twisted together, and may be pushed into a depression cast into the base of the bullet. The lubricant may be allowed to evaporate after the jacket has been applied; and a different lubricant may be applied after the formed paper has dried. Some very good accuracy has been obtained with paper-patched bullets, but the assembly procedure is relatively labor intensive. There is some question about whether the accuracy improvements result from the paper jackets or from the greater uniformity of shooting procedures by people with the patience to apply the patches. A relatively small number of shooters still load paper-patched bullets at velocities up to about 600 meters (2000 feet) per second.