Started shooting prairie dogs back in 1949 with a 22 RF rifle. Im 76 years old and started looking for a better varmint cartridge back then. Sofar I have used a 17 HM2, 17 HMR, 17 Fireball, 17 Rem, 204 Ruger, 22 RF, 22 WMR, 22 Hornet ,221 Fireball, 222 Rem, 223 Rem, 22-250 Rem, 220 Swift, 243 Win, and some of my big game rifles on varmints. I still have to try out the Hornady 17 Hornet and 5.7X28 MM. There are also some fine wildcat cartridges but Im not going to try them out. So Ill never know which varmint round is the best. But I like using the 17 HMR, 17 Fireball, and 204 Ruger rifles for prairie dog shooting and the 22-250 Rem, 220 Swift and 243 Win for shooting coyotes. It has ben fun reloading ammo and shooting what I got.