A shot tower is a tower designed for the production of small-diameter shot balls by free fall of molten lead, which is then caught in a water basin. The shot is primarily used for projectiles in shotguns, and for ballast, radiation shielding, and other applications for which small lead balls are useful.
In a shot tower, lead is heated until molten, then dropped through a copper sieve high in the tower. The liquid lead forms tiny spherical balls by surface tension, and solidifies as it falls. The partially cooled balls are caught at the floor of the tower in a water-filled basin. [1] The now fully cooled balls are checked for roundness and sorted by size; those that are "out of round" are remelted. A slightly inclined table is used for checking roundness. [2] To make larger shot sizes, a copper sieve with larger holes is used.
The maximum size is limited by the height of the tower, because larger shot sizes must fall farther to solidify. A shot tower with a 40-meter drop can produce up to #6 shot (nominally 2.4mm in diameter) while an 80-meter drop can produce #2 shot (nominally 3.8mm in diameter). [3] Polishing with a small amount of graphite is necessary for lubrication and to prevent oxidation.
The process was invented by William Watts of Bristol, England, and patented in 1782. [1] [4] The same year, Watts extended his house in Redcliffe to build the first shot tower. [5] Use of shot towers replaced earlier techniques of casting shot in moulds, which was expensive, or of dripping molten lead into water barrels, which produced insufficiently spherical balls. Large shot which could not be made by the shot tower was made by tumbling pieces of cut lead sheet in a barrel until round. [6]
The "wind tower" method, which used a blast of cold air to dramatically shorten the drop necessary and was patented in 1848 by the T.O LeRoy Company of New York City, [7] [8] meant that tall shot towers became unnecessary, but many were still constructed into the late 1880s, and two surviving examples date from 1916 and 1969. Since the 1960s the Bliemeister method has been used to make smaller shot sizes, and larger sizes are made by the cold swaging process of feeding calibrated lengths of wire into hemispherical dies and stamping them into spheres. [9]
A shotgun is a long-barreled firearm designed to shoot a straight-walled cartridge known as a shotshell, which usually discharges numerous small pellet-like spherical sub-projectiles called shot, or sometimes a single solid projectile called a slug. Shotguns are most commonly smoothbore firearms, meaning that their gun barrels have no rifling on the inner wall, but rifled barrels for shooting slugs are also available.
A cartridge or a round is a type of pre-assembled firearm ammunition packaging a projectile, a propellant substance and an ignition device (primer) within a metallic, paper, or plastic case that is precisely made to fit within the barrel chamber of a breechloading gun, for the practical purpose of convenient transportation and handling during shooting. Although in popular usage the term "bullet" is often informally used to refer to a complete cartridge, the correct usage only refers to the projectile.
Spray drying is a method of forming a dry powder from a liquid or slurry by rapidly drying with a hot gas. This is the preferred method of drying of many thermally-sensitive materials such as foods and pharmaceuticals, or materials which may require extremely consistent, fine particle size. Air is the heated drying medium; however, if the liquid is a flammable solvent such as ethanol or the product is oxygen-sensitive then nitrogen is used.
In guns, particularly firearms, caliber is the specified nominal internal diameter of the gun barrel bore – regardless of how or where the bore is measured and whether the finished bore matches that specification. It is measured in inches or in millimeters. In the United States it is expressed in hundredths of an inch; in the United Kingdom in thousandths; and elsewhere in millimeters. For example, a US "45 caliber" firearm has a barrel diameter of roughly 0.45 inches (11 mm). Barrel diameters can also be expressed using metric dimensions. For example, a "9 mm pistol" has a barrel diameter of about 9 millimeters. Since metric and US customary units do not convert evenly at this scale, metric conversions of caliber measured in decimal inches are typically approximations of the precise specifications in non-metric units, and vice versa.
A BB gun is a type of air gun designed to shoot metallic spherical projectiles called BBs, which are approximately the same size as BB-size lead birdshot used on shotguns. Modern BB guns usually have a smoothbore barrel with a 4.5 mm (0.177 in) caliber, and use steel balls that measure 4.3–4.4 mm (0.171–0.173 in) in diameter and 0.33–0.35 g (5.1–5.4 gr) in weight, usually zinc- or copper-plated for corrosion resistance. Some manufacturers still make the slightly larger traditional lead balls that weigh around 0.48–0.50 g (7.4–7.7 gr), which are generally intended for use in rifled barrels.
A shell, in a military context, is a projectile whose payload contains an explosive, incendiary, or other chemical filling. Originally it was called a bombshell, but "shell" has come to be unambiguous in a military context. Modern usage sometimes includes large solid kinetic projectiles, which are more properly termed shot. Solid shot may contain a pyrotechnic compound if a tracer or spotting charge is used.
A shotgun shell, shotshell or simply shell is a type of rimmed, cylindrical (straight-walled) cartridges used specifically in shotguns, and is typically loaded with numerous small, pellet-like spherical sub-projectiles called shot, fired through a smoothbore barrel with a tapered constriction at the muzzle to regulate the extent of scattering. A shell can sometimes also contain only a single large solid projectile known as a slug, sometimes fired through a rifled slug barrel. The hull usually consists of a paper or plastic tube often covered at the base by a metallic head cover which retains a primer, and the shot charge is typically contained by a wadding/sabot inside the case. The caliber of the shotshell is known as its gauge.
In current usage, a riot gun or less-lethal launcher is a type of firearm used to fire "non-lethal" or "less-lethal" ammunition for the purpose of suppressing riots or apprehending suspects with minimal harm or risk. Less-lethal launchers may be special purpose firearms designed for riot control use, or standard firearms, usually shotguns and grenade launchers, adapted for riot control use with appropriate ammunition. The ammunition is most commonly found in 12 gauge shotguns and 37mm or 40 mm grenade launchers.
A shotgun slug is a heavy projectile made of lead, copper, or other material and fired from a shotgun. Slugs are designed for hunting large game, and other uses, particularly in areas near human population where their short range and slow speed helps increase safety margin. The first effective modern shotgun slug was introduced by Wilhelm Brenneke in 1898, and his design remains in use today. Most shotgun slugs are designed to be fired through a cylinder bore, improved cylinder choke, rifled choke tubes, or fully rifled bores. Slugs differ from round ball lead projectiles in that they are stabilized in some manner.
A molecular sieve is a material with pores of uniform size. These pore diameters are similar in size to small molecules, and thus large molecules cannot enter or be adsorbed, while smaller molecules can. As a mixture of molecules migrates through the stationary bed of porous, semi-solid substance referred to as a sieve, the components of the highest molecular weight leave the bed first, followed by successively smaller molecules. Some molecular sieves are used in size-exclusion chromatography, a separation technique that sorts molecules based on their size. Other molecular sieves are used as desiccants.
The gauge of a firearm is a unit of measurement used to express the inner diameter of the barrel.
Shot is a collective term for small spheres or pellets, often made of lead. These have been projected from slings since ancient times and were the original projectiles for shotguns and are still fired primarily from shotguns and less commonly from riot guns and grenade launchers, although shot shells are available in many handgun calibers in a configuration called "birdshot", "rat shot", or "snake shot". Lead shot is also used for a variety of other purposes such as filling cavities with dense material for weight/balance. Some versions may be plated with other metals. Lead shot was originally made by pouring molten lead through screens into water, forming what was known as "swan shot", and, later, more economically mass-produced at higher quality using a shot tower. The Bliemeister method has supplanted the shot tower method since the early 1960s.
Continuous casting, also called strand casting, is the process whereby molten metal is solidified into a "semifinished" billet, bloom, or slab for subsequent rolling in the finishing mills. Prior to the introduction of continuous casting in the 1950s, steel was poured into stationary molds to form ingots. Since then, "continuous casting" has evolved to achieve improved yield, quality, productivity and cost efficiency. It allows lower-cost production of metal sections with better quality, due to the inherently lower costs of continuous, standardised production of a product, as well as providing increased control over the process through automation. This process is used most frequently to cast steel. Aluminium and copper are also continuously cast.
Spray forming, also known as spray casting, spray deposition and in-situ compaction, is a method of casting near net shape metal components with homogeneous microstructures via the deposition of semi-solid sprayed droplets onto a shaped substrate. In spray forming an alloy is melted, normally in an induction furnace, then the molten metal is slowly poured through a conical tundish into a small-bore ceramic nozzle. The molten metal exits the furnace as a thin free-falling stream and is broken up into droplets by an annular array of gas jets, and these droplets then proceed downwards, accelerated by the gas jets to impact onto a substrate. The process is arranged such that the droplets strike the substrate whilst in the semi-solid condition, this provides sufficient liquid fraction to 'stick' the solid fraction together. Deposition continues, gradually building up a spray formed billet of metal on the substrate.
The Sparks Shot Tower is a historic shot tower located at 129-131 Carpenter Street in Philadelphia, Pennsylvania. Opened on July 4, 1808, it was one of the first shot towers in the United States, with the Jackson Ferry Shot Tower in Wythe County, Virginia possibly predating it by a year or so. It was built near the Delaware River waterfront at Front and Carpenter Streets, just west of Gloria Dei Church.
A sieve analysis is a practice or procedure used in civil engineering and chemical engineering to assess the particle size distribution of a granular material by allowing the material to pass through a series of sieves of progressively smaller mesh size and weighing the amount of material that is stopped by each sieve as a fraction of the whole mass.
A choke is a tapered constriction of a firearm barrel at its muzzle end. Chokes are most commonly seen on shotguns, but are also used on some rifles, pistols, or even airguns. Notably, some .22 LR match rifles have a constricted bore diameter near the muzzle.
A paper cartridge is one of various types of small arms ammunition used before the advent of the metallic cartridge. These cartridges consisted of a paper cylinder or cone containing the bullet, gunpowder, and in some cases, a primer or a lubricating and anti-fouling agent. Combustible cartridges are paper cartridges that use paper treated with oxidizers to allow them to burn completely upon ignition.
Bearing balls are special highly spherical and smooth balls, most commonly used in ball bearings, but also used as components in things like freewheel mechanisms. The balls come in many different grades. These grades are defined by bodies such as the American Bearing Manufacturers Association (ABMA), a body which sets standards for the precision of bearing balls. They are manufactured in machines designed specially for the job.
A spray is a dynamic collection of drops dispersed in a gas. The process of forming a spray is known as atomization. A spray nozzle is the device used to generate a spray. The two main uses of sprays are to distribute material over a cross-section and to generate liquid surface area. There are thousands of applications in which sprays allow material to be used most efficiently. The spray characteristics required must be understood in order to select the most appropriate technology, optimal device and size.
