I have been shooting the .17HMR for about 8 or 9 years. I have a Marlin SS with a Leupold Compac 3x9. My experience with prairie dogs is very similiar to yours. I usually take my custom .220 Ackley Improved Swift too and anything over 125 to 150 is Swift territory. I've shot a couple of coyotes to. but this little bullet is just too damn small.The rimfire .17's are a hoot to shoot and pretty cheap shooting too. Have fun!!