I have killed 2 deer with a 22 magnum. Bullet weight doesn't have much to do with killing if the shot placement is perfect. We've got a lot of deer in AL, and a very liberal season until last year, when the state limited us to 3 bucks, but we can (not that anyone would want to) still legally kill 145 does each year. I've killed quite a few deer, most of them with a 7mm Rem mag. I recovered every deer I shot with the 7 mag, that I hit properly. The ones I didn't hit right, lost 80% of them. You can gut shoot a deer with a 300 Win Mag, and more times than not you won't find it. A 243 is a fine deer cartridge, but I don't understand why you would want to limit yourself to one weight bullet. Use a heavier built bullet during deer season, then switch over to a lighter bullet to shoot varmints.
And as someone else already stated a .224 55 grain bullet is a much different beast than a .243 55 grain bullet.