How do I repair the chamber flap on the Nerf Mega Magnus?

If you take the rifle apart, there is a place for a bunch of the safegaurds so you dont chop of your finger, the red safegaurd is what is blocking it, tap it, and the trigger should pull back

I had this problem too. You want to take the gun apart,remove the barrel and then take out the front orange piece.it separates into two parts and on the Inside is a screw and Spring,this controls the little plastic piece that slides up to stop the flap. you may need to tighten or loosen the screw,or just move the piece up and down a bit to loosen it up.