The .270 WSM was introduced in 2001. It is designed to give magnum performance in a .27 caliber cartridge that will work through a short action rifle. It is based on the very fat .300 WSM case necked down. The body of this case is so fat (.555 inch) that the magnum size .535 inch rim must be rebated (made smaller in diameter than the cartridge body) to allow the cartridge to work with a magnum size bolt face. The case length is 2.1 inches, and the overall cartridge length is 2.86 inches. The shoulder angle is a very sharp 35 degrees. Magazine capacity is reduced by one round compared to standard diameter magnum cartridges like the 7mm Remington Magnum. This ultra fat short magnum not only equals .270 Win. performance, it exceeds it. The ballistics of the .270 WSM falls between the ballistics of the standard .270 Win. and the powerful .270 Weatherby Magnum.
This text is based on information from “Cartridges of the
World”, Hodgdon reloading manual, the cartridge designer and/or