From The Manufacturer/Wikipedia/People Smarter Than Us:
Smith & Wesson’s Extra Large Frame (X) revolvers are the most powerful production and Performance Center revolvers ever built. The Model 460XVR™ was released in 2005 and sports the highest muzzle velocity of any production revolver on the planet. This handgun launches 200-grain, .460 S&W Magnum bullets at approximately 2,300 feet per second. The X-Frames come equipped with compensators to reduce felt recoil.