I have two AR's for coyote hunting, one is a rebuild DPMS, the other is a factory build Armalite.
The DPMS rebuild now has a 20 inch Criterion HBAR barrel, 223 Wylde chamber, 1in8 twist.
It's plenty accurate enough for coyotes, I practice shooting an 8 inch round plate at 300 yards, using my truck bed for support I hit the plate on most shots.
The Armalite is their VSR model (I highly recommend this rifle) with an 18 inch barrel, 223wylde chamber 1in8 twist.
This rifle is very accurate also, again I practice shooting the 8 inch plate at 300yards.
The ammo I'm shooting in both of these guns for practice is PMC Bronze 55gr FMJ, it's not the most accurate ammo I've used but for cheaper practice it does just fine.
For hunting I use 52gr match loaded by Black Hills, accuracy with this ammo is top shelf.
Best Regards
Bob Hunter