I have a CA sporty m4 and the the whole barrel rotates left and right a few degrees.
get it where you want it and dont touch it
"its god's job to judge the terrorist; its our job to arrange their meeting" -USMC- my senior quote
There are a few set screws that hold everything in place. The one you probably want is on the underside of the front sight post. Find a suitable hex wrench, line up the sight, and tighten it down. Bring it by AEX and we'll take care of it for you, if you like.