The .401 Winchester Self-Loading (also called .401SL or .401WSL) is an American rifle cartridge. Winchester introduced the .401SL in the Winchester '10 self-loading rifle as a supplement to the Winchester '07 and the .351SL in their offering of hi-power, self-loading rifles. The only chambering available in the Winchester Model 1910, the .401SL was used by France, Russia, and American company security forces in the First World War. The .401 Winchester self-loading, for comparison, is comparable in "stopping power", to a .41 Remington magnum fired from a similar length barrel.