Well any light caliber from 243 on up will work for sheep.Still i live in alaska and use a 8mm mag.Every time i am sheep hunting i run into grizzlys. At a 100 yds my 270 didnt feel bad, at 40 feet it felt small.
I shot my last ram at 450 yds with a 8mmRem mag, and 180 grain nosler BT.if ur not hunting in alaska, anything from 243 up is fine.
