The .351 Winchester Self-Loading (WSL) cartridge was introduced in 1907 by the Winchester Repeating Arms Company for use in their Winchester Model 1907 self-loading rifle. The cartridge features a straight, rimless case and fires a .352-inch diameter bullet, generally weighing between 180 and 200 grains. It was designed to provide greater stopping power than the previous .32 WSL and was intended for both law enforcement and civilian use, notably in semi-automatic rifles.
The .351 WSL cartridge saw some use by law enforcement and prison guards during the early 20th century, including in the United States and France. It was favored for its reliability and significant ballistic performance compared to other self-loading cartridges of the time. However, it eventually fell out of favor with the advent of more powerful cartridges and firearms. Today, it is considered obsolete, with limited availability of both the ammunition and rifles chambered for it, making it more of a collector's item.