Richard J. Casull was a Salt Lake City-born gunsmith and wildcat cartridge developer whose experiments with .45 Colt ammunition in the 1950s led to the creation of the .454 Casull cartridge. Casull's passion was six-shooters, and he was determined to create a high velocity round for the .45 Colt. His goal was to achieve a muzzle velocity of 2,000 feet per second with Colt .45 rounds fired from a single-action Army-style revolver with a 7+1⁄2inch barrel. This proved impossible due to the tensile strength of the Colt .45 cylinder, so he set out to develop his own casing and bullet.

A wildcat cartridge, often shortened to wildcat, is a custom cartridge for which ammunition and/or firearms are not mass-produced. These cartridges are often created in order to optimize a certain performance characteristic of an existing commercial cartridge, or may merely be intended as novelty items.