The .401 Winchester Self-Loading (WSL) cartridge was introduced by Winchester Repeating Arms Company in 1910. Designed for use in the Winchester Model 1910 self-loading rifle, it was intended primarily for hunting medium to large game. The .401 WSL fires a 200 or 250-grain bullet at a muzzle velocity of around 2140 feet per second (for the 200-grain bullet). This provided substantial stopping power for its time.
The semi-automatic Model 1910 rifle chambered in .401 WSL was somewhat popular among hunters for its rapid follow-up shot capability compared to bolt-action rifles of the same era. Despite its robust performance, the cartridge and the rifles chambered for it saw limited success and were eventually overshadowed by other cartridges and firearm technologies.
Today, the .401 WSL is considered obsolete, and ammunition is difficult to obtain, typically only found through specialty manufacturers or handloading by enthusiasts. It remains a cartridge of historical interest rather than practical use in modern hunting or shooting sports.