Well, I was reading reply to reply untill it drifted off topic. Here in TN they have started allowing .223 for deer.
I have taken 5 deer with my 16" ( really SHORT!ballistically speaking) Ar. I'm loading really hot loads to get the velocity back up to compensate for short barrel.
I have shot 2 buck deer out at 200 yards, and they both went straight down, and never moved.(65 grain S,GK BTSP @ 2900 fps) My coyote load is a 60 grain Varmint bullet 2950 fps.
At 400 yards, from my short barrel my AR is delivering as much energy as a GI .45acp at the muzzle.Easily enough for a dog or deer. It's about shot placement, always has been, alwys will be.
400 yards is my limit on deer.(With my 16" AR) I have no limit on Dogs, I don't like them, they eat fawn & polt.
Exactly like Shakey yankee said, Get a scope with a reticle that is usable at range. Learn it intimatly. Learn your rifle & load's dope, intimatly. Learn to identify wind speeds in field conditions. You only have to get it approximate for short range shooting (inside 600 yards.)
And shoot 60 grain + bullets, they drift less and retain more energy.
Research & learn: This country has an epedimic of misinformation about firearms & ballistics, generally it is a belief that the system is capable for far less than it is.. The Rifleman is a dying breed. Research & learn, for example:
What is an MOA? How big is it at 300 yards? at 679? At 1351?
What is a Mil? (Milradian) How big is it at 211 yards? at 687? at 1561?
How do convert from Mil to MOA and back?
How do you compensate for a 54 degree down hill shot? What about a 29 degree up?
What does a 20 degree temp change do to your zero at range?
What is a quartering wind? How do you figure for it? (Not "common sense," you guessed wrong)
What is density altitiude? Why should you care?
The range, of any given firearm is only limited to the guy driving it. Don't settle to be grandma, holding traffic up!