Bottom line a .223 will kill an elk but the difference is more than 0.019 diameter.

Using the previous example provided

.223/ 62 gr - at 3100 fps carries a kinetic energy of 1323 ft/lbs
.243/ 95 gr - at 2980 fps carries a kinetic energy of 1873 ft/lbs

There's 42% more energy being imparted on the elk between a 243 and a 223.


Deal with it.