When the groundhogs overran our farm in the 80's, I started taking a 10-22 with me on the tractor and using regular CCI Mini-Mag and WW 22LR hollowpoints. It usually took multiple solid hits to anchor one. Then tried CCI Stingers and they worked a lot better, BUT I learned that shot placement was still important. Out to around 100yds, I could kill 'em fairly reliably with one shot through the shoulder/lungs/heart area or the neck or head, but if running away from me, it still took several "Texas Heart Shots" with the Stingers to stop one and often they still made it to their dens.
After a while, they got smarter and I started having to carry a centerfire to reach out to them.
In '02 my job took me to rural northern Missouri and I made friends with several local farmers/ranchers who asked me to kill the groundhogs on their property. The 17 HMR craze was in full swing then, and I bought a CZ up there. It was a death ray out to around 150yds, but I still had to pay attention to shot placement. About anything behind the rib cage would result in a crawl-off, unless my German Shepherd got to 'em first. He would grab, shake and retrieve.
Out west, I found that rock chucks have about the same tenacity as groundhogs, but, on average, were harder to recover because of their closer proximity to their dens or other hidey-holes and cover. Out to around 150yds, the 17 HMR will anchor 'em pretty well if you punch 'em through the shoulders, neck or noggin.
