The .327 Federal Magnum is a cartridge introduced by Sturm, Ruger and Federal Cartridge, intended to provide the power of a .357 Magnum in six shot, compact revolvers, whose cylinders would otherwise only hold 5 rounds.f you want more than the .327 delivers, you have to go to the .357 Magnum, and having done so you will pay mightily for it. An SP101 in .357 delivers a 125-grain JHP at more than 1,300 fps, but you get only five shots and muzzle blast and recoil that could make a brass monkey flinch.