Try the search function. There have been several threads this month on this very same topic.
Last year I shot 3 foxes with the 223 40gr Vmax. A neck shot nearly decapitated one fox. Yes that's where I was aiming. The other two vitals shots looked like what happens when you stomp on a banana... The peel splits open and the insides spill out. Same thing happened with the foxes, not explosions or splash wounds, but the force split the hides open from the inside and ruined them, just like a squashed banana.
There's not much to a fox, I think the 17hmr is perfect for them, my longest shot last year was 155 yards DRT instant kill.
I plan on trying a 223 69gr Sierra Match King this year to see how it does. I think a non expanding or more solid bullet will do less damage than a Vmax type varmint bullet if you want to save pelts.
I called in 39 foxes last year, some came in really close early in the season and hung around. Those could have eadily been taken with a 22lr. But the majority would have been very difficult shots with a 22lr and tracking a runner would be nearly impossible in the brushy areas they like. For me it's DRT or nothing.
Aim small miss small.