TKO Value is of limited usefulness. It mainly favors mass and diameter rather than energy as it was created to calculate effect on dangerous game species. It takes into account that the .30-.378 Weatherby and the .458 Win has similar muzzle energies, but one is clearly more useful for Cape Buffalo. In such situations, the TKO Value is more useful than energy alone.
Clearly, here, this is not the case.
The .45 has a good reputation for being effective, for an automatic handgun cartridge. But it is still an automatic handgun cartridge. Even from a carbine, the damage it produces is significantly less than the .223.
It has to do with the fact that most tissue is elastic enough to absorb shock occurring under a certain velocity threshold (around 2000 fps), without permanent damage. With handguns, all that matters is the depth and width of the permanent wound channel, that is, tissue displaced by the bullet itself. The .223 is a whole different animal. It has enough velocity to damage tissue for several inches beyond the path of the bullet. This means that with the .45 you have an expanded projectile diameter of .65 to .85 inches, in most cases, and a penetration of 11 to 14 inches. The .223 is going to penetrate about the same, but is at distances experience in home defense, is going to yaw and fragment, and tissue displaced not only by the projectile and its fragments but also by the shock forces they produce are going to be damaged. So while the wound channels are of equal depth, the largest .45 wound channels are going to be an inch in diameter at the most, even out of a carbine, while the width of the wound channel produced by the .223 is more than likely going to be several inches.
The .223 is orders of magnitude more effective than the .45. Never forget that handguns are handguns, and rifles are rifles.
