In the past 4 years I've shot around 7,000 rounds of HMR and Mach2 during my prairie dog hunts. And I shot a coyote with a 17 HMR. My furthest shot with the HMR on a prairie dog was 283 yards. But since the bullet drops below sonic velocity the effect was significantly less than when the bullet is still super sonic.
Neither the HMR or the Mach2 is going to have the same affect on a ground hog as if you shot it with a high velocity 223 varmint bullet. But it is still going to be dead. I shoot a lot of the pd's in the chest and I will see them head for the mound with blood pumping out like a deer shot through the chest. And they normally fun out of life after going several feet. Shot in the head the results are more dramatic.
Most of my shots on pd's with the mach2 are out to around 175 yards. With the HMR I routinely shoot them out to 250 yards. The HMR provides somewhat better accuracy and of course higher velocity. But the mach2 is no slouch.
A frequent shot I get is a pd looking over the top of the mound. All that is visible is the eye and the portion of the head above that. This is what the HMR does on that shot.
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