How tight should the barrel, or barrel extension be when you insert it into the upper receiver? I tried 3 uppers already with my bushmaster stainless barrel but they have a little "play' or "wiggle" when i insert barrel. unlike with my other builds, you need to make a firm tap to insert barrel extension to upper.
will this be totally eliminated when the free float handguard is tightened/ or will this slop fit cause accuracy problems?

I have always had a snug fit on my BK,FK and key hole uppers.