If you have a .243, there's your varmint rig. If you have a .300 Win Mag, there is your elk rifle. If you are looking to shoot a bunch of varmints with a .25-06, wear a recoil pad. If you want to shoot deer and elk at all practical ranges, get a .270 WSM. It is a bit much for varmints, though.

Good Dogwork and Good Hunting