At the risk of being chastized for interrupting a bullet construction and expansion debate...
To the op... What is your skill level / shooting experience / comfort level... In my opinion, get a 30.06 or a .308 and be done with it.... Worry about all this nonsense when you get used to harvesting game with the 30 cals.... I'm not a 30/30 fan but if it's all you have use it and take responsible shots.... No need to try and do the long range stuff with a .243.... Much better out there (including the two above) for that purpose...
Range time between 20 and 40 times a year for rifle, mostly offhand shooting at 50 m with .22LR, .223. Once in awhile I'll bring out something larger. Been shooting off and on for about 25 years up until a few years ago when I started going regularly, but never at longer ranges than about 250 m. I can hold about 2-3" off hand at 50 m, 6-8" off-hand at 100 m, and with any rest I can shoot probably half that. Benched I can shoot less than 1/2 MOA. Prone with a .222 sporter last year at 200 m (250?) was about a 4-6" group (wasn't my gun). I need to practice 3P at 200 and 300 m. I like the sitting position best - easy and quicker to plant my butt and get a good rest with a sling. I don't plan on off-hand shooting at game unless very close, and I rarely ever have. I think this attitude would make me effective out to about 250 m.
I haven't hunted in many years but am planning to do so in the near future. I haven't shot my first deer - it was mostly small game back then and I got skunked for the seasons I went deer hunting. I have .243 and .30-30, and the question came up as a means of identifying redundancy in the safe. I also have .270, .308, .30-06, .338, .375 H&H and like them. As you can tell, redundancy isn't something I control well.

The notion is perhaps to turf the lever action and stick with bolt actions of the same model, thereby becoming a pretty good shot with any of them. Practice with one will feed into the others. So I thought maybe sell the .30-30 and use the .243 bolt action for a bush gun. The other thought was to load the .308 with 170 grain .30-30 bullets and get the same performance. But if the .243 will do fine then it's good out to my self-imposed hunting range.
Hunting-wise, I would probably keep my shots to 250 m or less depending on my rest. Probably would pass up most things over 200 m and try to stalk closer. Again, I did a poll on here awhile back and 95% of all big game shots were taken under 200 m, so I'm not really worried about all the long range banter. More concerned about matching the round to the game within my chosen parameters.
I'd like to see how the average FTR competitor groups at 600 and 800 meters on paper in ideal conditions with a rest with a 14 pound 30" bull-barreled .308, Nightforce Hubble Special with external adjustments, wind flags, known ranges, known declinations, and target ammo. Take this ideal and then change to a 7-8 pound sporting rifle with a lighter barrel and a heavier trigger, your pack or your knees for a rest, 3-9x40mm or 4x scope, weather, wind, bushes, tall grass and trees, bouncing walking moving breathing deer with real animal lives who could really suffer if you #### it up, and all the excitement and trepidation that goes along with that shot, and I think that it's appropriate to give the poor thing a good margin of safety on shooting it. At the very least, we owe the animal that. Of course when I'm a pro 600 m shot who can guesstimate wind, I might think differently.