Fx Crown question.

I went to clean my barrel and I went to removed the shroud and notice my barrel was turning. The barrel. So I tighten it back up, barrel is tight now. And I check the set screws and they are tight. Like I can’t turn them. Why could make the barrel turn. I seen a picture that Tomcat had when he removed his barrel and I was wondering if the barrel screws onto the silver section or is that the same piece. 

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