[rifleman8]

I'm guessing the intended condition for the 90 series flash hider is as tight as it will go with the "point" of the spring retainer sitting down in a groove between two spline teeth - even if that is not real tight. I'm also guessing lots of you fine folks have better info/knowledge than my goofy guesses - by all means chime in - Thanks

 

[Steve_in_29]

Tight as you can get it with the retainer in a groove, even if you have to back off to the last groove you just passed if it won't tighten enough to make the next one is correct.

 

[Heavy Artillery]

Hands tighten; no tools required.