There are two versions of the M&P15T, which one do you have?
I didnt realise they had more than one version, so Im not sure which version I have. I got it a couple of years back.
The play in my sights is most noticeable front to back, but there is also some side wiggle as well. As I said earlier, they shoot "OK", its just they dont seem to be as repeatable as the GG&G's, which have zero play.
This is my M&P15T....
and the sights....