Accuracy and reliability are opposite ends of the measure.

An extremely accurate rifle will be one with a tight "match" chamber, light "match" trigger, stainless barrel, and fine match sights or optics.

An extremely reliable rifle will be one with a mil-spec chamber, hard hitting trigger, chrome lined barrel, and stock rugged iron sights.

A stainless barrel can be [i]marginally[/i] more accurate. Chromelined barrels are easier to clean and longer lasting (and mil-spec).

The Bushmaster would be the one I would recommend from your choices. The Armalite could be a tad more accurate but will cost plenty more. By the time you're able to shoot the rifle to that level you'll know better. The Colt will run you lots more than either of the other two and not shoot one bit better. It will sell for more used as newbies recognize "Colt".

I own Armalites, Bushmasters, Olympic Arms, a DMPS and a even a poorly made Hesse.