First off...if you're in Southern Ontario and need your groundhogs dispatched~that's as easy as sending me a PM! 
As for what you need~.22WMR would cover you up to the coyote application, but isn't (in my opinion) enough to kill them reliably. Granted, a poorly-placed hit from a .223 wouldn't be good either. Since you're asking about a gun/caliber and NOT a hobby~my vote would have to be .223. I'd say .204 R, but .223 is WAY easier to find (factory ammo) and less expensive as well. If you want to add a hobby that is a bit expensive to set-up for, reloading would help you feed that K-Hornet reliably, and it sounds like a dandy gun for what you need it for.
As for what you need~.22WMR would cover you up to the coyote application, but isn't (in my opinion) enough to kill them reliably. Granted, a poorly-placed hit from a .223 wouldn't be good either. Since you're asking about a gun/caliber and NOT a hobby~my vote would have to be .223. I'd say .204 R, but .223 is WAY easier to find (factory ammo) and less expensive as well. If you want to add a hobby that is a bit expensive to set-up for, reloading would help you feed that K-Hornet reliably, and it sounds like a dandy gun for what you need it for.


















































