An AR is really the only autoloading platform that is accurate enough to take advantage of the .223's range. However, you are looking at spending over $1,000 by the time you get the gun and top it with a decent scope.

You can get a bolt gun for about half that, top it with a good scope, and still save a couple hundred bucks. And the accuracy of most bolt guns is as good or better than a lot of AR's.

The .223 round itself is great for coyotes. Ammo is cheap, there is a wide selection of loadings to choose from, and it is widely available. A .223 will kill coyotes futher than most shooters can accurately shoot.