Champ, to some extent all centerfire cartridges with the possible exception of the older, slower rounds like the .22 Hornet, 218 Bee, etc, are going to be hard on fox. Fox are light, thin skinned, and they are going to blow up easily with the wrong hit from a centerfire. Foxes are not very hard to kill, when he was growing up my father used to shoot them very effectively with his 20 gauge and bird shot because that's all he had.
The best case scenario with fox is to shoot them right through the rib cage with a non-ballistic tip bullet and hope the bullet passes cleanly through. I would use a traditional soft point or spire point, not a plastic BT like the VMmax.
The best fox solution, IMO, is to carry a shotgun and a rifle and only use the rifle if you absolutely have to. I do this quite often when calling more open areas. I sit with the shotgun across my lap and the rifle beside me up on a bipod.
Shotguns whack foxes dead, they just do so by putting 6-8 small holes in vs one big hole. To me that's the ideal solution, messing around with bullet choice makes only a marginal difference at best.
Grouse