if i shot my ar and the dust cover was shut would it shoot and the cover would open....JOE

It'll open when your rack the charging handle to chamber the first round.  But if you closed it again after that, yes, the bolt carrier will pop it open when you fire the first round.

Hey Joe,

   PLEASE get someone in your area who is experienced to take you to a range and shoot the AR.  The Black Rifle will become simple to understand and use. Until then hold off on the BLASTIN'.  I intend no disrespect.  Education and training are necessary.

OK.
Look on the right side of he bolt carrier. See the about 1" oval shaped indention with 2 holes in it?

This groove is their for the rounded protruding piece in the center of the ejection port cover.
It rides inside the groove. When charged, the bolt carrier will ride along the till the center piece of the ejection door cover hits the edge popping it open. Same if the door is closed and you fire a round.