RE: gun for fox
220 is a only a slightly SLIGHTLY hotter round than a 22-250. The 220 swift is more expensive...and both will destroy a fox's hide
If you're in it for pelts I would echoes everyone advice to look at the 17s and 22hornet, heck I'd even look at 22mag, and 22lr if I knew they'd be within 100(and capable of head shots)