I think the aforementioned .260 Rem is the perfect answer here, followed closely by the 6.5x55 Swede, .257 Roberts, 7x57 Mauser and 7mm-08. All of these rounds are about as perfect a round as can be devised for shooting deer at 300 yards or less.

Of these, the 7mm-08 probably tops the list, but it may be too much overlap with the 7mm mag.

Good Dogwork and Good Hunting