I shoot many Fox with .308 deer loads, Core Lokt bullets. Mid chest just behind the shoulders (lungs), the vast majority are hole in, hole out, very little damage. I avoid areas with a lot of bone, shoulder, head ect. Neck or lungs is your best bet.
Gut shots are to be avoided, they usually make a grizzly mess. A head on shot may also explode the guts.
Smaller animals I use a shotgun, with rifles they tend to explode.