Shot tower

A shot tower is a tower designed for the production of shot balls by freefall of molten lead, which is then caught in a water basin. The shot is used for projectiles in firearms.

Shot making

Process

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, then solidifies as it falls. The partially cooled balls are caught at the floor of the tower in a water-filled basin. 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. To make larger shot sizes, a copper sieve with larger holes is used. However, the maximum size is limited by the height of the tower, because larger shot sizes must fall farther to cool. A polishing with a slight amount of graphite is necessary for lubrication and to prevent oxidation.

History

The process was invented by William Watts of Bristol, UK, and patented in 1782. The same year, Watts extended his house in Redcliffe, Bristol to build the first shot tower. Shot towers replaced the 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 were made by tumbling pieces of cut lead sheet in a barrel until round.

Shot Tower (Dubuque)

The Shot Tower located in Dubuque, Iowa, is one of the last remaining shot towers in the United States. It is listed on the National Register of Historic Places and remains a recognized symbol of the city. At its location near the Mississippi River, the Tower can be seen from the riverwalk and is currently undergoing extensive renovations. It stands 120 feet 5 inches (36.70 m) tall.

History

The tower was built in 1856 to provide lead shot for the military. The invention of the shot tower enabled economical production of many nearly perfect lead spheres of the right size to fit in a musket. To make the shot, molten lead was poured through a grate at the top of the tower. The droplets that fell from the grate were of relatively uniform size, and the fall provided enough time for the liquid-metal droplet to form into a sphere before landing in the water below. The water cooled the lead to its solid state, retaining the spherical shape.

The shot tower struggled almost immediately due to economic downturn from the Panic of 1857. When the Civil War broke, the Union Army purchased shot from towers in St. Louis, Missouri. A St. Louis company, Chadbourne & Co., purchased the Dubuque tower, but did not use it. After the war, the Standard Lumber Company used it as a fire watchtower.

Jackson Ferry Shot Tower

The Jackson Ferry Shot Tower is 75-foot (23 m) tall shot tower located in Wythe County, Virginia. It is one of only a few remaining shot towers in the United States. It was built by Thomas Jackson and is the centerpiece of the Shot Tower Historical State Park. Construction began on the tower shortly after the American Revolutionary War and was completed in 1807. It was listed on the National Register of Historic Places on October 1, 1969.

Purpose

Shot Towers were often referred to as Shot Factories during the industry's heyday. Today they stand as testaments to ingenious yet antiquated technology. The purpose of the shot tower was to produce lead shot to be used in firearms. Firewood and lead were taken to the top of the tower, where a furnace was fired to melt the lead. The molten lead was then poured through a sieve, which would form individual drops of lead of a specific size. Different sieves were used to produce shot of varying size. The molten drops would then free-fall 150 feet, during which they would become spherical in shape, and cool enough to become rigid. A large kettle full of water at the bottom would finish the cooling process, and provide a soft enough landing to keep the shot from deforming. The finished shot was then sold to hunters, traders and merchants.