IMHO, there is a strategy in harvesting groundhogs that works in conjunction with the .22LR selection. These are curious critters. Jays Sporting Good (a sports shop in Clare, MI) used to sell swinging, armor-plate steel, silhouette targets of groundhogs. They were life-size.
I had my Ruger 10/22 HB zeroed at 225 yards, using a 4X target-turreted scope. This rig, with Remington Thunderbolts, consistently was grouping in the 2" range at 225 yards (off the bench). I would set the steel target a few yards from the groundhogs' entrances. Then, I would insert the 10-round magazine and plink the steel silhouette 2 or 3 times. As I sat there waiting, the groundhogs almost always would start to pop out and look to see what was causing the noise.
As the groundhogs came out and stood on rear legs to look, I would take my shot. I save the most important for last. The silhouette looked real (shape). I placed it between the collective entrances and the sun. As the sun provided (I believe) some hindrance to see if the target was real, fellow groundhog, or if it was something else. When they would stand up, I would take a head-shot or neck-shot. The rationale for shooting to the head or neck was two-fold: 1) I would hit or I would miss…small target, and 2) if hit, it would be fatal because all tissue therein is vital, period. A body-shot may or may not be fatal. I never had to make 2 shots on these groundhogs. All dropped where they stood.
I usually either sat at the picnic table, under a tree and behind the grapevine. This way, sitting and waiting for hours on end was comfortable. Sometimes I would stalk closer, 150 to 175 yards, and wait. Having the target turrets, and a cheat-sheet for the trajectory really helped. In closing, the Thunderbolts worked incredibly well, provinding complete penetration each and every time, and rendering "instant results".