243 has plenty of energy for deer past 500 even with 95gr bullets. Get some trigger time and a decent scope and it will do fine.
A 165 gr. .308 (.30-'06) has approximately 50% more kinetic energy at 400 yards than a .95 gr. .243, with a bullet like a Winchester silver tip.
Kinetic energy doesn’t kill stuff.
That's about as naive a statement as I've seen on here. If a hunter is going to shoot an animal at 400 yards, he had better have adequate energy to compensate for less than perfect shot placement. If the round he is shooting has minimal energy to do the job, then he had better be very selective in the shots he takes...............and most hunters are NOT. And, the .243 falls into the category of minimal kinetic energy to kill a deer at 400 yards with perfect shot placement.
Read this:
Kinetic energy, the ability to do work (or in this case damage), is the most common measure of killing power for rifle bullets.
https://www.chuckhawks.com/rifle_bullet_killing_power.htm
Cut and paste from the article:
Energy and killing power"Kinetic energy, the ability to do work (or in this case damage), is the most common measure of killing power for rifle bullets. And it is, in fact, a reasonable indicator. But it is by no means the only factor, or even the most important factor. Energy gives us an idea of how much power there is to initiate things like bullet expansion and penetration, but does not guarantee that they will occur.
It is generally recommended that a small bore (.24-.32 caliber) rifle bullet suitable for medium size (CXP2 class) game be carrying about 800 ft. lbs. of kinetic energy when it hits. Energy is greatest at the muzzle, and diminishes as the bullet loses velocity. When the velocity reaches zero, so does the energy. But long before that the bullet has fallen below the recommended level of energy for reliably killing deer size animals. So the practical hunting range of any cartridge is ultimately limited by how much energy remains. (It is also limited by other factors, for example trajectory, but that is another subject.)
As an example, let's take a .30-30 rifle firing a Federal factory load with a 150 grain bullet at a muzzle velocity of 2,390 fps. At the muzzle that bullet carries 1,900 ft. lbs. of energy. At 100 yards the energy has fallen to 1,355 ft. lbs. At 200 yards the energy is down to 945 ft. lbs. At 300 yards the energy has fallen to only 650 ft. lbs., which is below our 800 ft. lb. minimum. The velocity, by the way, is down to 1400 fps at 300 yards. One could conclude that the .30-30 is about a 200+ yard deer cartridge, based on its energy, and one would be right."
800ft/lb is the
recommended amount of energy, so by that it could also be said
needing anymore energy means you should practice more so you stop taking terrible shots and relying on the rifle for your ineptitude. Also, Nosler Trophy Grade 243 with 90gr Accubonds carries 923ft/lb at 400 yards. So even according to the article, the 243 is completely up to the job so long as you do some practice.