well I have shot them with .338 ultra mag and down to .22's
bigger isn't always needed
a .223 is plenty, BUT you have to be using the right bullets and well, shot placement
bigger and faster will help a small amount on bad shot placement but is not the solution to the running off problem
are you using Ball .223 ammo, if so thats a big problems right there
you can get some heavy .223 loads that will make a bigger impact, and or you can get better heads in general and reload for what ranges most of your shots are being taken at
too light too fast too solid a tip up close ior far can seriously effect how a bullet performs on a hit!
if your taking head shots, shouldn't matter LOl
but if your shooting them like a deer behind the shoulder, bullet selection is huge deal all the more so UP close, and real far off!
I have killed yotes with a .223 dropped in tracks at 550+ yrds, and as close at about 25 feet
and all the ranges in between
so caliber is fine, its bullets and shot placements
you can sure kill them with bigger calibers, but its not needed
if you want to go bigger upper, I would suggest a .243, or the new 6.8
great calibers, and can then go as a deer gun too, but to be honest, if your thinking a .223 is light for yotes, then these claibers in that thinking make them light for deer!
again sure they will kill deer with right bullet and range and shot placement
but if a .223 is light for yotes then you will need a .30 + cal for deer with that logic
not bashing, just saying
killed a lot of yotes dead in there tracks with a .22 short over the yrs, hit in the head at 50 so yards, no problem!