I've been involved in too many 243 rodeos started by other shooters to bother with it. It is pointless. What I've seen is the 223 does what 243 does. 243 does work with good shooting, but it isn't better than 223. I've never seen anyone shoot a 243 better than a 223 or worse than any of the 308-class .25s or 6.5s wth lighter bullets. So, you may as well step up to the surer performance of a larger caliber and faster cartridge. There's no penalty and everything to gain.

Couple facts, to help:

New 223 bullets over 60gr will amaze you. A fast twist barrel is required, but most people have one now in their AR. For youth shooters your AR is perfect. They don't kick like lightweight 243s do and they kill just as well.

If you use the same powder charge with the same bullet weight in a smaller caliber, you will get less velocity. It's pushing with your hand instead of your shoulder.

So much work has been put into bullet design in the last ten years that you can find effective, reliable deer bullets at lighter weights than before. If you're going to use a 243 because you want a 100gr bullet you may as well use a 25 or 6.5 100gr. It'll be bigger and faster with negligible increase in recoil. A person who likes the way a 243 handles will be better off with 120gr .260 or 7mm08. A good 120gr 6.5mm bullet will do everything you may need on a whitetail.