In 1949 I started shooting prairie dogs with a 22 RF rifle. Since then I have tried to find the perfect varmint cartridge . I v used 17 HM2, 17 HMR, 17 Hornet, 17 Fireball, 17 Rem, 204 Ruger, 22 LR RF, 22 WMR, 22 Hornet, 221 Fireball, 222 Rem, 223 Rem, 22-250 Rem, 220 Swift , and 243 Win. rifles...