My two fox specific guns are a Sako 75 Hunter in .17 Rem and a Remington 597 in .17 Hmr. Both reliably anchor foxes within their effective ranges. However, a 17 Rem will make hamburger out of them if they're too close.

Why no love for the 17 hmr? Shocking! lol. Great little fox round imo. Foxes are tiny and the 20 grain CCI gamepoint puts 'em down for the count out to 125 or so. YMMV