I have 4 cartridges in mind. The first two being more popular and finding ammo being much easier, they are the .25-06 and .243 Winchester. The others which I am thinking of would be the .257 Roberts and the 6mm Remington. I think all four of those cartridges would fill the bill quite nicely. Only problem with the last two is that ammo can be a pain to find, and there are few offerings for them in factory rifles nowadays. So, I guess stick with either the .25-06 or .243 (25-06

).