.
450 Bushmaster
.404 Jeffery
.358 Winchester
6.5mm Grendel
OH and something that shoots, patched .530 round ball, but the topic is "center fire" so this last choice would be off topic.
WHY the above four? Well there are lots of nice cartridges that I also like, such as the .35 Whelen, .30-06 Springfield, .45-70 Government, 6.5 Creedmoore, 7mm-08 Winchester, .25-06, .243 Winchester, etc etc.
I chose the
.450 Bushmaster because it's a straight walled cartridge that is therefore allowed for deer in areas where straight walled cartridges are the only rifle ammo allowed for deer, and it is available in both bolt action and AR-15 platforms, while something like the .45-70 Government although being also a straight walled cartridge, is a "long action" so lever action and bolt action and the odd single shot rifle. The .350 Legend would also work. Even the .44 Magnum would suit, but not in an AR platform.
I chose the
.404 Jeffery, which was a purely academic choice, because it was well liked in Africa for very dangerous game, by the rangers and the guides, while the hunters were using something larger in many cases. I figure the professionals know or knew something. It would be my African cartridge, but it's only "on paper" for me. The .416 Lott is another contender. This was only from reading, and my sources could be outdated or even full of beans, eh?
The .
358 Winchester because it is easily fabricated from .308 brass, is good in bolt action and lever actions rifles, and IF somebody made a barrel for it, you could put it in a AR type of platform.
Finally the
6.5 Grendel as it out performs 5.56 NATO/.223 Remington in an AR-15 platform, and it's lower pressure than a lot of the cartridges that also work in the AR-15 platform and out perform the 5.56 NATO/.223 Remington, as well as I have personal experience with it and like it.
.530 patched, round ball as that allows me to hunt during Muzzle Loader season as well as regular deer season with a flintlock that will perform when primers and caps are scarce.
LD