barm,
I am not a big groundhog hunter and I do not own a .204, but in my area of Virginia 300 yards will get you to most any groundhog and I would think the 204 would be fine for that. If your .223 is accurate enough that would be my groundhog rife to 300 yards though.
If in your area if you shoot more than 300 yards you may want to ditch the .204 and keep the 22-250. Where I live in Virginia the coyotes have taken a toll on the groundhogs.
