I bought one of the Armalite AR180B rifles some years back. Other than some minor break in issues, it has been trouble free, and is quite accurate.
I have not experienced any failures, or problems of any kind. The chamber is tight, and you need to clean the receiver well, but other than that its good.
I did have the intregal muzzle brake cut off, and the barrel crowned and threaded to take an AR birdcage.
Currently, I am using a Bushnell red dot sight, but I have other optics options I can put on the rifle.