My daughter uses an old Remington 788 in 243 Win. She's killed a many a deer with none "lost". I have all the confidence in the world in a well placed 243 Win. round using any of the 100 gr. quality bullets .... as already mentioned, the Sierra Game King is a good one. So is the Partition.

No doubt a 7mm. (.270) or larger hunting bullet moving at the same or higher velocity = a bigger wound channel and maybe better penetration. But for deer, the 243 Win. is fine.