A fellow that I knew through work was introducing his son to elk hunting. I think his sone was 14 yoa and average build. they decided that a 243 Win with handloads of 95 gr Nosler Partitions was perfect elk medicine. the area they hunted was public land that bordered on private where no hunting was allowed. the son took-up his stand on a trail that led down from the private land. Opening morning shortly after shooting light a spike elk came down the trail out of the private land. The son fired one shot. the elk fell down and was dead by the time the sone got to it.
For the next several months we heard nothing but heckling about how our group was over-gunned (.30-06, 30/338, 300 Win & 300 Wby). How we needlessly destroyed meat and absorbed excessive recoil.
The next year came. The son took his 243 & Nosler bullets to his spot nest to the private land and just like the previous year a spike elk came walking down the trail just after light. Just like the previous year the son fired one shot, but this year the elk dropped to his front knees, then bounced back up and started running. Since it was public land there were other hunters and shots fired. the elk dropped after a run of several dozen yards. the son ran after the elk and when he arrived another hunter had tagged it. the hunter claimed the elk was running and after he shot the elk fell so it was his. an argument ensued between the son, father and the other hunter, but the other hunter claimed the entire elk.
The nest several months we still heard about what great elk medicine the 243 was, but also what a bunch of jerks other hunters were.
The third year was a repeat of the second- shot fired, elk down then up & ran; mores shots and claimed by another hunter. We didn't hear much about the 243 for elk.
The fourth year, the son is now 17, but when he went hunting the 243 stayed at home and he was absorbing the excessive recoil of a 30-06. I transferred to a different area before I heard how the results of the hunt. But if it were me and I had a 243 to use for deer I'd opt for something of larger bore for the bigger animals.