I dug this A2 upper out of my parts bin. First thing I noticed is the rear sight. The whole assembly is cocked to the left and there is some play in it. Is it missing something? I'm not an expert in A2 sights.

Pics

That is normal and acceptable. There's a spring-loaded detent that presses against the "ear" of the upper receiver and keeps the sight assembly in the correct place. My first rifle was a 20" A2 from Model 1, and upon noticing this, I asked the person who at the time was supposed to be an expert in AR's bout it. He told me to send it back. Waste of my time as it was promptly returned to me because nothing was wrong.

ETA: I will add that it's annoying to look at, but you'll get over it once you see that it isn't an issue. I actually haven't even paid any attention to my new A2 build to see the amount of cant in the rear sight.

Seen lots like that in the arms room.  Normal


CD

Thanks for the info guys. I'm on the fence about building it out or selling it, just wanted to make sure it was not defective either way.

If it really bothers you send it to White Oak and they can pin it

If it really bothers you send it to White Oak and they can pin it

Spring tension is moving it.  You can pin it or drill (it's hardened so need a good bit)  identical hole in other side and install spring and detent ball to even it up.  Really isn't imperative unless shooting for pin point accuracy at variable distances.  Either mod will instantly make it a better shooter without doing much else if using elevation knob.  Never was designed to be much better than 4 MOA with M-855 / SS109 or that's milspec.