From the mid-18th to late 19th century, Napoleonic use of cannon was a common practice among the armies of America and Europe. Artillery corps were directed to place their cannons in a position where they could deal the most damage to infantry, and new and more devastating forms of ammunition were developed to maximise each cannon's effectiveness. By the mid-19th century, minor fortifications and lines of infantry faced artillery ammunition geared specifically toward their destruction on the battlefield.
Development of Grapeshot
When field artillery was used in earnest in the early 18th century, commanders experimented with different forms of ammunition to improve on the minimal damage caused by traditional single, large balls of lead. In large cannons, several balls from a smaller calibre cannon were strung together with fabric and rope. The success of this assembly led to the development of specifically designed rounds of grapeshot, with three to eight smaller lead balls ranging in size from 1/3 to 1/10 of the cannon's full-sized solid ball.
Uses of Grapeshot
Although originally developed for use against infantry, grapeshot proved very useful against protected short-range targets. Consequently, grapeshot was often used by navies, where each shot had to have a maximum chance of striking a target and causing major damage. In this respect, single balls could easily miss, whereas grapeshot's multiple balls stood a much greater chance of striking a short or medium-range target while still causing significant damage. Grapeshot also led to the use of chain shot, a variant in which each ball was connected by chain and caused massive damage to ships' sails and rigging.
Development of Canister
As artillerymen noticed that smaller variants of grapeshot caused a greater spread of damage at shorter range, they began to experiment with smaller and smaller balls. Eventually, small musket balls were simply loaded into a cannon atop the powder charge, creating a spread out but very short killing zone of 10 to 75 yards. The best anti-infantry size was found to be 1.5-inch balls loaded in a tin can, which flew apart when fired. These balls carried lethal velocity up to their maximum range, and could even pass through several bodies at short range.
Uses of Canister
While grapeshot was still sparingly used against infantry, by the mid-19th century it had almost been completely replaced as anti-personnel ammunition by canister. At medium to long range, grapeshot had a somewhat greater range than canister, but the advent of case shot -- hollow balls that exploded at range -- made this use of grapeshot obsolete. At short range, there was nothing more devastating against infantry than canister, which could even be double-loaded if the need arose.