Richard J. Casull (/kəˈsuːl/) (February 15, 1931 – May 6, 2018) 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.