Weatherby Mag and Coastie:
The correct obscure calibers are either the 257 Newton or 30 Newton.
How can you have a screen name like that and not say .270 Win? Saying .308 made Jack O'Connor roll over in his grave.
The OP asked for the caliber for Mulies and WT deer. Personally, I think the 30-06 is overgunning, espcially when considering the little deer of the historic deep south and east coast states. That is why I said a .25 caliber. No doubt a 257 Roberts will stop and Mulie too.