As member 22Dasher noted above:" the .22cal will win". BUT ya gotta give it sufficient barrel length to compete against the larger bore size!
For the sake of conversation & comparison, here's some stats from my .224cal (coyote capable) rifles, shooting the same weight bullet...
.223AI, 26" barrel: 75Amax @ 3105fps
.22-243, 27" barrel: 75Amax @ 3550fps, 75VLD @3620fps
.22-243AI, 27" barrel, 75Amax @ 3600fps
.220Redline, 27" barrel, 75JLK @ 3975fps
To compare, my 6x47L, 23"barrel, shoots a 105Hybrid @ 3002fps, and 87Vmax @ 3185fps.
Going UP in bore size ain't doing squat to improve MPBR, nor is the heavier bullet weight. And hamstringing MV from the shorter barrel only makes it worse!
When you're talking coyote killing, ideally, you choose the combo that allows for most ballistic 'forgiveness'. I.e, the flattest trajectory MPBR with which help to correct for distance guesstimates & critter size. Least that's my rationale, anyway? Going heavier in caliber runs contrary to that logic, when ya run the numbers...
The only thing is, when ya neck down a parent case in hopes of achieving increased MBPR, you've gotta allow for a few extra inches of barrel to eeek out the velocity that allows for that luxury. Note, the barrel lengths on my 'hotrods' listed above...
Assuming the same parent case, larger bore size will most always be more 'efficient'. This is due to the same powder charge (pressure) doing 'work' against more bullet surface area. Think of a hydraulic piston running at equal psi, but one with a larger ram to push against. The increased surface area allows the same force (case pressure) to be distributed more efficiently...
This is why you can sorta, kinda, get away with a shorter barrel with a larger bore, and not suffer the velocity penalty as the same case, necked down. Make sense?
But, when you're seeking optimal performance, you can kick efficiency to the curb! Efficiency gets almost ZERO consideration when ya wanna go fast. My .223AI is getting by on a mere ~26grains of powder, whereas the Redline is gobbling up ~65grains. So ya can see how foolhardy it would be for me to argue 'efficiency' when striving for ballistic superiority...
So, to re-hash, if ya wanna neck down (any) .264 or .243cal parent case for coyotes, I'm 100% in agreement with that logic! Coyotes die plenty well from even .172cal bullets (with enough MV), so a .224cal (with enough MV) can quite literally 'overkill' a 20-50lb. canine. The key is in getting "enough" velocity to make the pixie dust fly!
Given that, skimping on barrel length runs contrary to the logic of necking down in the first place...
Something to muse over, anyway! Have fun deciding!
