Re: 500 yard rig
Personally, they're both good. But I would look at the .22-250 in a Savage, they make them in a 1:12" twist (if you're lookin' to shoot the lighter bullets) then maybe improve the chamber to AI. That would be a pretty hard gun to beat, and would have a ballistic edge over the .204 (wind drift is what really matters, especially at the ranges you are talking, drop is easy to compensate for, as it is much more of a constant variable). I have a 1:12" 22-250 (not AI, yet haha), and if the wind is decent, I shot hits are regular at a 6"x6" plate at 400-450 yds.