I've killed dozens of deer with a 243win at ranges from 20yd or so to over 400 I've never failed to recover a single one of them and never had one run more than 100yd tops. Just behind the shoulder shots which resulted in DRT on all but 3. Of them it was with the 100gr cor-lock I blame not shot placement. I assure you I can hold minute of deer vitals too wayyy out there. First example was at about 30yd bullet gave great splash effect but no blood trail and the deer made it about 40yd before piling up. The second was about 120yd and she made it about 100yd down hill to die. In both cases I waited about an hr before trying to recover "I didn't push the animal in any way". I was confident with my shot in each case and knew the animal was hit, and hit hard. I don't like the inconsistent results I've gotten with that load, exit wounds would vary greatly from animal to animal.
I did shoot one large built deer for my area he was 220lb field dressed he was hit 25-30yd right behind the shoulder quarter slightly away the bullet hit right where I was aiming and stopped just under the skin on the far side. He ran about 15 steps to his death, he was dead and never knew what hit him, vitals were quite literally juiced. I will never shoot a 100gr cor-lock again I've found a more consistent loads that I have more confidence in Hornady 95gr sst, and recently with 96gr Berger vld so far love the results.
Regardless of caliber shot placement is king period!!! The newest wiz bang magnum may give you a touch more margin for error but, you'll not shoot it as well because of the recoil and cost to get the practice you need. I can and have shot three or four boxes in one sitting with a 243win with no ill repercussions to my shoulder or developing a flinch. The heaviest recoiling gun I have is a 7mmrem mag, it's hell on everything I've shot with it but, it's not fun to shoot. I will never sit down and fire more than one box of ammo from it before I see I'm tensing up and not taking my time to break each shot.
There are people out there who can fire a magnum all day and if you are one of them I applaud you for it you're a better man than I. Heavy recoil is not my thing. Will a 243win kill everything from whistle pigs to elk just as dead as the biggest baddest magnum? With proper bullet selection and shot placement yes it will. I'm not going to chase a big brown bear or hunt african game with one because there are better choices for that, for deer the "little" 243 is just fine. It will do it with less cost and punishment than a heavy magnum and the ability to shoot more, which means more practice and that's always a good thing.
My first deer rifle was a Ruger m77 243 with a 3-9x40 Leupold Dad bought me when I was 12-13 it has killed more game than anything I own except maybe my 20ga 870. "I've had that since I was 10 or so". I've got bigger rifles that shoot a little flatter or faster and have more energy than my "little" 243 and I will shoot them because they take a little less adjustment for distance and give me a little more margin for error. Are there "better" calibers for uber long range deer killing out there yes, are there smaller caliber which will work up close yes. Would I shoot elk at 600yd with "my" 243 no, I've got a 7mag with a bigger scope which will do that just fine, once again giving me a little more "wiggle" room. Will I give anyone crap for doing it with "their" 243 nope, if they've taken the time and got the confidence to do it go for it.
Bottom line; if you know your gun and shoot the right bullet the "little" 243win will kill deer quickly and reliably. May not give you the DRT results which we all like every time but, you show me a caliber/bullet combo that will without exclusively taking head shots.
Good luck and happy hunting.
I was 15-16 when I killed this buck he was definitely dead enough when I got to him.