What kind of gun should I use?

I live in an area where there is a large field behind my house(yes we do own the property) and this area contains multiple groundhogs. Now we have a few guns but they either shoot too far or not far enough... I would probably end up shooting 100 to 200 yds but if I have a little extra distance it my help but the gun needs to shoot under 300 yds. Wat caliber gun should I use? I thought a 22 would work but I want to keep it under a 243