I'm using a custom AR in .223 AI, and it's performed pretty well to the 500 yd. mark with 1 dog at 550 on a very calm afternoon. I believe the effective range to be about 500 yds. in my experience. I've probably killed about 4 or 5 dogs at that range. It won't kill them instantly at that range most of the time with thru the lung hits, but they won't last very long. I wouldn't try and shoot 1 at that range when he's close to the top of a hill tho without snow in sagebrush country. He'll get far enuf away he may be hard to find. I think the 69's are good to that range, and the 55/60 gr. polymer tips will do it in no wind scenarios with the right setup.
My load shoots the 65 JLK Low Drag (BC-.4) @ 3050 mv., and has only killed 1 dog at 500 (that was a quick gut shot and had to be finished off). 400 is not a problem with an established system. 10 mph wind to about 300-350, and maybe 5 mph beyond that tho that's still tough @ 500. I use ballistic reticles - calcd., checked, troubleshot if necessary, rechecked and then dope is placed in the ocular cover of a Butler Creek scope cap cover for quick reference/protection.
My favorite optic/ballistic reticle for this application is the 22 Long Rifle Rapid Reticle right here-- http://www.rapidreticle.com/22lr3-9x32.htm recalcd. for the trajectory of my load, as it gives me good windage reference. There are certainly others that will work fine, certainly some (Horus Vision) i haven't tried. My favorite factory ballistic reticle is the Varmint Hunter again based on the excellent direct windage reference.
Shooting coyotes at long-range is not a matter of buying a ballistic-reticled, target-turretted scope and zeroing it at 100 yds. and then expect to hit coyotes @ 400-600 yds. with any degree of consistency. It's an education and learned discipline that opens a door to the most fascinating type of shooting you'll ever do...but the right to shoot game at long-range needs to be earned through a lot of study and practice and is not something approached whimsically.