.223 / 5.56 for deer hunting?

[Double K]

Most folks in Colorado wouldn't dream of hunting deer with a 223, many are shot at 250yds or farther where the 223 is below 1000lb lbs of energy.
I'm putting together a 6mm arc to hunt coyotes and doe deer/antelope, it's an AR-15, it has plenty of energy out to 300yds for smallish big game 125lbs or less.

 

[doofus47]

I'm thinking that a lot of regs are "rule of thumb" efforts to make life easy for field agents. For example, the Colorado regulation forbidding big game hunting with a cartridge under 24 caliber is probably so the CPW agent can easily make a call in the field.
Probably when the dept. set that law the 222/223 was already available, but they said "Yeah, that could work, but then there's overlap with a lot of other .22s, so... 24 we go!"

 

[Double K]

There's a huge variation of the size of deer throughout the US, because of the climate the farther north you are the bigger the deer are, I travel to Texas and Tennessee occasionally, the deer look like the size of great danes to me.
You don't shoot deer this size with varmint rifles, it's not ethical and a 22caliber bullet would blow up if you hit him on the point of the shoulder never making it into the vitals.
In my backyard a couple of years ago, yes that buck has an extra antler growing out the side of his head.