As has been said above, define it by bullet not by calibre or chambering, the answer will come from that.
Fox - if you want a specialist bullet because you do a lot of lamping then a 50 to 70 grain Blitzking is hard to beat. If it's just the odd fox then shoot it with your deer bullet.
Muntjac and Roe - no need to go above the 100 grain legal minimum for E&W - many will suggest you might slip below it.
What will shoot both bullets? 6mm. Roll on the "which 6mm" argument but the no brainer is a 243 Win.
Fox - if you want a specialist bullet because you do a lot of lamping then a 50 to 70 grain Blitzking is hard to beat. If it's just the odd fox then shoot it with your deer bullet.
Muntjac and Roe - no need to go above the 100 grain legal minimum for E&W - many will suggest you might slip below it.
What will shoot both bullets? 6mm. Roll on the "which 6mm" argument but the no brainer is a 243 Win.