The 224 Weatherby Magnum or "Varmintmaster" was introduced in 1963 following at least a decade of experimentation by Roy Weatherby, who wanted a fast 22 centerfire in his line of Weatherby Magnum cartridges. The 224 Weatherby Magnum is a unique cartridge; with a .429-inch rim diameter it is the smallest of all belted cartridge, and of course has Weatherby's distinct "double-Venturi" shoulder. Actual velocity, however, is similar to the 22-250, with 50-grain bullets running about 3800 feet per second. Only Weatherby has made the ammunition, and few rifles other than Weatherby's have been chambered to it. -- Craig Boddington