 Sierra bullets are used for precision target shooting, hunting and defense purposes.Available calibers range from .204 (suitable for the .204 Ruger) through to .500 (suitable for the .500 S&W Magnum).In the late 1940s, three aircraft machinists, Frank Snow, Jim Spivey and Loren Harbor, rented space from Clint Harris in the Harris Machine Shop in Whittier, California to produce precision rivets for the aircraft industry, along with fishing rod guides and rifle front sight ramps.