Ladies and Gents:
I'm building an upper.  In assembling the rear sight, I noticed that the diagram shows a rear sight elevation spring.  My kit doesn't have the spring.  What's surprising is that the rear sight on my Bushmaster A-2 factory upper doesn't have the spring either!  The sights seem to work OK without the spring in place.  Can anyone tell me if they stopped using it?  Also, if you'll check your uppers next time you have the bolt carrier out, I wonder if others' ARs are also sans spring?TIA
VR
Vinny D

I suppose the elevation index detent pushes the sight in the right direction but there really should be an elevation spring in there.  If I were you I'd pick some up and install them.  They are cheap.