Your theory is sound.....sounds like something a politician would say that is!! This coming from the guy who once convinced a group of college faculty that riding a bike is more dangerous than riding a bull. Ain' t statistics wonderful!!!

For one thing, your model, as in all physics, uses an idealized environment and denys things that are vital to inclusion and includes things of slight fallacy.

Firstly, a .223 bullet is lucky to retain 60% of its mass upon exiting a coyote, while a .416 bullet used for CB' s are designed to retain 80% or better (and usually do unless a bone is impacted) of their mass. If both would stop in the body, 100% of the velocity is lost, while if the .223 loses 50% of it' s mass, it loses energy twice as quickly, but, truth be told, it' s much more quickly, since force=mass*velocity, if the velocity decreases by 50% per half-second, and the bullet fragments in half per half second, your energy after the first half-second is 1/4 of what you had upon impact. With a .416, losing 20% of it' s energy per half-second, and the same 50% of it' s velocity per half-second, the resultant energy at the end of the first half-second is 2/5 of the initial value, nearly twice that of the .223' s retention.

If you have a 70gr bullet (.00455Kg) @3000fps (914.4m/s), you yield 4.16Newtons (metric equivalent to ft.lbs.). A 400gr bullet (.026Kg) @2500fps (762m/s) you yield 19.8Newtons, so you have about 4 3/4 times as much energy in the 416rigby, no surprise, my tables have 70gr (.21BC)@3000fps at 1399ft.lbs. and a 400gr (.38BC) @2500fps at 5552ft.lbs., about 4 times the energy in the .416rigby.

What does damage in a high-powered round is the hydrostatic shockwave. If the energy is enough, the CNS will be vibrated to a point of shutting down, commonly known as knocking them in the dirt, the bullet will appear to simply knock them over and nothing moves (other than a small nervous twitch, but the game' s already dead). In both of these rounds used on these game animals, the energy isn' t enough to shut down the CNS, but the shockwave still does the damage. Shooting something with a high powered round is kind of like knocking over the first dominoe in a 1-2-3-4...etc pyramid, one knocks down the next two, and they knock down the next three, and the next four, etc. So, what really gets affected initially is dependant on the face area of the bullet, a .416 spire point bullet can easily have the same face area as a .223 wadcutter even, so the area effected by a round nosed bullet in used in each round would be 3.5times greater in the .416 (.136 vs .0391).

Now, a Cape Buff. might weigh 2000# and a white tailed deer might weigh 150# (both are fairly inaccurate, 2000# is a heck of a bull, and a 150# deer' s a greyhound with a rack or a two year old doe), but as far as it goes, the bullet doesn' t have to affect the entire body to do the deed. The only mass that must be affected is a straight line from the entry point to the vitals, not the tail, nor the nose. A bullet pushes a conical section of semi-viscous liquid (soft tissue). It' s a fair assumption that a cape buffalo is twice as deep to the heart, and I' d imagine that it' s maybe 1.5times as heavy per pound than a deer, even it it were 2 times as heavy per pound, the conical section of soft tissue that would have to be affected would be less than four times as heavy in a CB than in a deer, so with four times the energy and less than four times the mass, the more energy would reach the vitals of a CB than a deer.

So with a .223, you have a shattering bullet inflicting a quarter of the energy upon impact and exponentially decaying in energy every instant after impact, while with the .416, you might be pushing a bit more mass, energy retention is such that the penetration and hydrostatic shock is MUCH more with the big dog than the mouse-fart.