OK cp, maybe your serious, but I feel like I'm being set up here.
You wrote;
"Example:
.223 Remington, 55gr @ 3100fps = 1172 ft-lb energy
.45 Long Colt, 255gr @ 860fps = 418 ft-lb energy
.223 is virtually guaranteed to stay inside an elk whereas the .45 LC has a very good chance of going clear through."
To just go over the basics with you, speed is measured in feet per second, or fps. As a general rule of thumb, the faster the bullet travels, the flater it shoots and the more accurate it is. Basically the faster the bullet travels, the sooner it gets to it's target and the less time it's being pulled down by gravity.
Next we look at bullet size. A small bullet holds very little energy in it with less impact on objects it comes into contact with. The faster you move the bullet, the more energy it will have. Your example of the .223 witha 55 grain bullet only has 1,172 pounds of energy.
Energy is determined by speed of the bullet and the bullet weight. You can tweek this with bullet design and powder burn speeds, but we'll stick with the basics. Energy is the amount of power the bullet hits the target with.
This isn't very much energy. In fact, it's only going to be effective for hundred pound animals or less. Very few hunters will consider this a big game hunting cartridge. It will kill a deer under ideal conditions, at close range with a very good shot, but that is very unlikely in the real world.
The other example in your comparison is the .45 only has 418 pounds of energy. This will still hurt a human sized target, but it would be a very, very poor choice for hunting. Plust this is a pistol cartridge.
Comparing a low speed pistol caliber to a high speed rifle round is just silly. There is no other term to describe it. But to prove that you are trying to make some sort of joke, you chose an elk as your example. An animal that weighs 800 pounds or more, and is the second strongest, toughest animals in North America. The only animal bigger and stronger are the big bears. A moose will weigh more, but doesn't even compare in strength.
Neither caliber in your comparison has much of a chance of killing an elk at one hundred yards. In fact, the pistol will barely break the skin. The only shot that has any chance of killing an elk with a 45 is going to be through the eye socket at such an angle to take out the brain. Even then, I'd have my doubts. The 223 might make it to the heart, or puncture a lung, but the damage will be so minimal that he'll travel miles before dying.
These are realistic expectations of what those calibers are gonna do. Neither has a chance of going through an elk, but he 45 will be lucky to make it to the elk even is he's at the close range of 100 yards.
Your only argument for killing an elk with a 45 is if it's tied up and in a cage. Then you can kill an elk with a .45, but the bullet still wont have enough power to travel through the animals.
If you have an interest in learning about weapons, or ballistics, just do a google search on the term, "rifle ballistics" or " bullet ballsitics" and you will find all the numbers. Then we can debate which is the best elk caliber until we die and never come up with an answer. There are some calibers that are better suited to elk hunting over other calibers, but that just limits the debate to about a dozen or so calibers.
As an example, here are your ballistics and I've added my two hunting rifles.
.223 Remington, 55gr @ 3100fps = 1172 ft-lb energy
.45 Long Colt, 255gr @ 860fps = 418 ft-lb energy
.30-06 Springfield, 165 gr @ 2800 fps = 2872 ft-lb energy
.338 Winchester Magnum, 250 gr @ 2660 fps = 3927 ft-lb energy
I use the .30-06 for hogs, deer, caribou, pronghorn, sheep and animals in the 100 to 400 pound range. Notice that it has 2.45 times the energy of the .223 and 6.87 times the energy of the 45. This is a caliber that will kill an elk, but not one I'd recomend. It also isn't powerful enough to put a bullet through an elk. At one hundred yards, it will kill, but at 300 yards, the energy drop is too significant to be effective or reliable. When hunting elk, cross canyon shots are very common.
The .338 mag is my elk caliber. It is 9.39 times more powerful than the 45, it's 3.35 more powerful than the .223 and 37 percent more poweful than my .30-06. This caliber will put a bullet through an elk. It is a belted magnum that is very, very powerful. My furthest elk kill with this caliber was right around 500 yards. It was a very, very far shot, but I was able to lie down with a very solid rest for the shot. I've killed four bull elk that had 5 points or better with this caliber. Twice the bullets passed all the way through.
When you say a bullet with 418 pounds of energy has more power than one with 1172 pounds, you are either being silly, making a joke, or don't have a clue.
When you say the slower, less powerful bullet has a better chance of penetrating an elk over a more powerful round, you just confirm my earlier statement.
The fact that you didn't even know that neither a slow pistol round, nor a fast, small caliber round can not pass through an elk tells me you might actually fall into the last catagory, and are offering opinions based on zero knowledge of what you are talking about.
Eddie