I think a 243 does it’s best work on medium game if we step up to a premium bullet like the Barnes TSX or the Nosler Partition.
My two failures to kill involved standard cup in core bullets.
The only issue with premium( hard) bullets in the 243( or pretty much anything), is they can make smaller wound channels than softer, standard cup in core designs.
This problem is exasperated in a small bore.
Because of where I live, I have killed literally hundreds of hogs and deer in my 50 years of hunting them. Power does matter, I killed 90 deer with a 300 win magnum before the first one went more than 5 yards. He went 10.
Killed about as many with a 270 Weatherby with the same results.
The Hornady Interlock that failed in the 243, was awesome in the 270 and 300.
I don’t use magnums much anymore, but something in the power class of a 308 just kills quicker than the 243 in my experience.
Your mileage may vary.