I have fired almost 20,000 rounds of 17HMR at prairie dogs. Several at fox, coyote, badger, a snapping turtle, and woodchucks.
On the larger than rodent critters, limit your range and pick your shots. On prairie dogs, depending on wind, shots to 300 yards will kill them just fine, but at closer ranges it is far more effective.
On a badger, myself and a close friend hit one in the fore head at least six times, it just shook them off and went back down it's hole. Clearly it was not enough gun.
The snapping turtle was a different story. It was my first serious encounter with a charging animal and here is my story.
It was a hot and sunny summer afternoon when I first spotted him crossing my yard, as our eyes met, he gave me that look like I owed him money and he was here to collect it. He turned directly toward me and I knew the fight was on. Being that snappers can't cover ground very quickly, I had time to walk inside my house and open the gun safe to pick a suitable rifle for the fight. The 416 Blaser? Too much I thought, my 308 Blaser? Might still be over kill. One of my many AR15'?, I won't have time for a second shot. So the next rifle in the rack was my first 17 HMR, a CZ with a four power Leupold scope. That would be enough, I'll just use the 20gr XTP loads I thought.
As I walked back to my deck, I could see he was still coming headlong for me, looking even madder than before. I set up the rifle and to my surprise, the snapper started a hard left turn away. As he changed his path from a direct charge to a hard left, I though perhaps it was over, but then remembered that as my old Air Cavalry Commander once told me; "Once the attack has started, you must close with and kill the enemy, or he will come back to fight another day".
So I took the shot, cross hairs resting on his right eye, good thing I did not have to lead him much. When the shot broke, he collapsed as if the Hammer of Thor had struck him. But how was this? With the adrenaline dump I jerked the shot in my panic and I should have hit him in the shoulder. Could my scope have been knocked off? Was my call bad? Has the muzzle been nicked?
Well I walked up and circled around behind him, remembering it's the dead ones that will kill you, ready to pay the insurance. It was then I noticed an entry hole his right shoulder, and the exit hole on the left. He was clearly dead. Further investigation reviled it was a through and through shot, on call, that the 20gr XTP did a wonderful job on the way through, and clearly it's a bullet you can count on to stop a hard shelled 40 pound Iowa snapping turtle.
The moral of the story is you will be just fine with a 17HMR on most varmints. Just don't loose your cool like I almost did, or you might not live to tell the tale.