The .243 is a high-velocity cartridge and as-such performs at its best with bullets under 100 grains. I've used a lot of 85 and 90 grain bullets with great satisfaction. A bullet designed for deer, but 90 grain weight or less is great for not only deer, but maintains flat trajectory for smaller animals beyond 300 yards. I handload and rarely use any factory ammo. The cartridge, used by my grandkids for deer, has taken some nice Maine bucks and does out to over 200 yards with one shot each. The cartridge's greatest traits are it's flat trajectory and decent velocity/energy.
I tend to use it for larger varmints like coyotes, bobcats, coons, and porcupines, but it will kill bears at shorter ranges, if necessary. When I first got a rifle in that chambering, I set up a target to sight-in at about 100 yards, using a rock wall as an angled backstop. I fired the first shot and a huge hole appeared in the target, that was mounted on a piece of cardboard. There was a bullet hole, of course, but also, another, about 1 1/2" in size and oddly shaped. It came from the rock that was hit by the bullet passing through the target and plastic-cardboard backer, about 15 feet from where the bullet struck a stone in the wall. Excuse me, but that impressed the heck out of me as to the cartridge's power!!! It's quickly killed several deer by teen grandsons and daughters and I wouldn't balk at using it for deer, should I ever need to. It seems to me that bullets of 100 grains and heavier reduce the cartridge's effective trajectory/velocity to kill smaller but tough animals. Velocity kills!!!! Flat trajectory helps to hit kill zones at various un-measured distances.
Your opinions/data are also valued, since I haven't had a plethora of experience with the cartridge on larger game, since my go-to deer rifles are .270s.
